The rapidly moving events raised the question of whether a rift had opened between Mubarak and the military command over the uprising demanding the president's resignation. Hours earlier, a council of the military's top generals announced it had stepped in to secure the country, and a senior commander announced to protesters in Cairo's Tahrir Square that all their demands would soon be met, raising cries of victory that Mubarak was on his way out.
Several hundred thousand had packed into Tahrir Square, ecstatic with expectation that Mubarak would announce his resignation in his nighttime address. Instead, they watched in shocked silence as he spoke, holding their foreheads in anger and disbelief. Some broke into tears. Others waved their shoes in the air in contempt. After the speech, they broke into chants of "Leave, leave, leave."
Organizers called for even larger protests on Friday. After Mubarak's speech, around 2,000 marched on the state television headquarters several blocks away from Tahrir, guarded by the military with barbed wire and tanks. "They are the liars," the crowd shouted, pointing at the building, chanting, "We won't leave, they will leave."
Hundreds more massed outside Mubarak's main administrative palace, Oruba, miles away from Tahrir in the Cairo district of Heliopolis, the first time protesters have marched on it, according to witnesses and TV reports. The residence where Mubarak normally stays when he is in Cairo is inside the palace, though it was not known if he was there.
Prominent reform advocate and Nobel Peace laureate Mohamed ElBaradei, whose supporters were among the organizers of the 17-day-old wave of protests, issued a Tweet warning: "Egypt will explode."
"The army must save the country now," he said. "I call on the Egyptian army to immediately interfere to rescue Egypt. The credibility of the army is on the line."
President Barack Obama appeared dismayed by Mubarak's announcement. He said in a statement that it was not clear that an "immediate, meaningful" transition to democracy was taking place and warned that too many Egyptians are not convinced that the government is serious about making genuine change.
"The Egyptian government must put forward a credible, concrete and unequivocal path toward genuine democracy, and they have not yet seized that opportunity," Obama said.
Hours before Mubarak's speech, the military made moves that had all the markings of a coup.
The military's Supreme Council, headed by Defense Minister Field Marshal Hussein Tantawi, announced on state TV that it was in permanent session, a status that it takes only in times of war. It said it was exploring "what measures and arrangements could be made to safeguard the nation, its achievements and the ambitions of its great people." That suggested Tantawi and his generals were now in charge of the country.
The statement was labeled "Communique No. 1," language that also suggests a military coup.
Footage on state TV showed Tantawi chairing the council with his chief of state Gen. Sami Anan and around two dozen of his topmost generals, sitting stern-faced around a table. Mubarak and Suleiman, a former army general and intelligence chief named to his post after the protests erupted Jan. 25, were not present, the strongest indication during the day of a rift.
But there was no immediate reaction from the military following Mubarak's speech, and their position remained ambiguous.
In his address on state TV, Mubarak showed the strategy he has followed throughout the days of upheaval, trying to defuse the greatest challenge ever to his nearly three-decade authoritarian rule. So far, he has made a series of largely superficial concessions while resolutely sticking to his refusal to step down immediately or allow steps that would undermine the grip of his regime.
Looking frail but speaking in a determined voice, Mubarak spoke as if he were still in charge, saying he was "adamant to continue to shoulder my responsibility to protect the constitution and safeguard the interests of the people." He vowed that he would remain in the country and said he was addressing the youth in Tahrir as "the president of the republic."
Even after delegating authority to his vice president, Mubarak retains his powers to request constitutional amendments and dissolve parliament or the Cabinet. The constitution allows the president to transfer his other authorities if he is unable to carry out his duties "due to any temporary obstacle."
"I saw fit to delegate the authorities of the president to the vice president, as dictated in the constitution," he said.
Suleiman was already leading the regime's efforts to deal with the crisis, though he has failed to ease the protests, which have only escalated in size and ambition, drawing crowds of up to a quarter-million people. In the past 48 hours they flared even further out of control, with labor protests erupting around the country and riots breaking out as impoverished Egyptians attacked and set fire to several police and governor headquarters in cities outside Cairo.
Mubarak insisted on the continuation of a government-dominated process for reform that Suleiman drew up and that protesters have roundly rejected because they fear it will mean only cosmetic change and not real democracy. Under that system, a panel of judges and lawyers put together by Suleiman recommends constitutional changes, while a separate panel monitors to ensure that state promises are carried out.
Suleiman has also offered dialogue with the protesters and opposition over the nature of reforms. He has not explained how the negotiations fit in if the judges panel, which is led by Mubarak supporters, is recommending amendments. In any case, the protesters and opposition have resolutely refused talks until Mubarak goes.
Mubarak called the protesters' demands legitimate and promised that September presidential elections - in which he says he will not run - will be "free and fair" with supervision to ensure transparency.
He said that on the recommendation of the panel, he had requested the amendment of five articles of the constitution to loosen the now restrictive conditions on who can run for president, to restore judicial supervision of elections, and to impose term limits on the presidency.
He also annulled a constitutional article that gives the president the right to order a military trial for civilians accused of terrorism. He said that step would "clear the way" for eventually scrapping a hated emergency law but with a major caveat - "once security and stability are restored."
The emergency law, imposed when Mubarak came to power in 1981, gives police virtually unlimited powers of arrest.
Before the night's dramatic developments, protests had gained a spiraling momentum, fueled by labor strikes that erupted around the country. Protesters had been gearing up for even more massive demonstrations on Friday, when they planned to march from squares around Cairo into Tahrir.
After the speech, some protesters drifted out of Tahrir, tears of disappointment and anger in their eyes.
But the majority of the crowd remained, camping through the night and vowing to continue their campaign.
"We are waiting for a strong reaction from the army to Mubarak's speech," said Mohammed Mustapha, a protest spokesman. He said "huge numbers" of protesters were expected Friday and that many wanted to march on the Oruba palace, Mubarak's main presidential palace several miles away from Tahrir - though so far organizers had not made a formal call to do so.
The mood among protesters was a mix of fury, disappointment, determination to go on and a grim realism that they should have expected little else from Mubarak.
"This will push the country to the edge of the abyss. Tomorrow, the army will intervene, if it does not, there will be chaos," said one activist, Waleed el-Korumi. "We will lay waste to our country if we march on the palace. It's a case of both sides sticking to its guns and at the end we will lose our nation," he said, though he added that marches would remain peaceful.
Muhammed Abdul Rahman, a 26-year-old lawyer who had joined the protesters for the first time Thursday called Mubarak's speech a "provocation."
"This is going to bring people together more, and people will come out in greater numbers," he said.
The shock of Mubarak's speech came after a roller-coaster day for the protest movement. In the past two days, what began as an Internet campaign that swelled into mass protests had seemed to tap into the deep well of anger among Egyptians over economic woes like corruption, rampant poverty, unemployment and vast disparities between rich and poor.
Labor strikes spread furiously across the country in wide breadth of sectors - postal workers, electricity staff and service technicians at the Suez Canal, in factories manufacturing textiles, steel and beverages and hospitals. A strike by bus drivers and public transport workers Thursday snarled Cairo's traffic.
Slum dwellers angry over housing shortages stormed the police headquarters and set it ablaze in the Suez Canal city of Port Said. In the south, farmers angry over bread shortages blocked roads with flaming palm trees.
The unrest grew to the extent that Suleiman and his foreign minister warned a coup could take place. And Thursday evening it seemed that was happened. Gen. Hassan al-Roueini, military commander for the Cairo area, went to Tahrir and told protesters, "All your demands will be met today,"
The protesters lifted al-Roueini onto their shoulders and carried him around the square, shouting, "the army, the people one hand." Some in the crowd held up their hands in V-for-victory signs.
But Mubarak's words came as a splash of cold water.
"The speech showed contempt for the demands and wishes of the youth," said one activist, Khaled Sayed. "People took it very objectively. We will keep up the pressure continue in Tahrir until we get what we want."
AP correspondents Maggie Michael, Hadeel al-Shalchi, Paul Schemm, Lee Keath and Marjorie Olster.