Updated at 9:37 a.m. Eastern
DAMASCUS, Syria Syrian President Bashar Assad said his civil war-ravaged country "will defend itself against any aggression" in the face of rising expectations of a punitive military strike by Western powers, according to Syria's state news agency.
The U.S. and other nations believe Assad's government is responsible for suspected poison gas attacks near Damascus last week. The group Doctors Without Borders says the attacks killed 355 people.
President Obamathat the U.S. is moving toward a punitive strike, saying there "need to be international consequences" for the deadly attacks.
Mr. Obama said although he hasn't made a decision on the exact response, any strike would be limited in nature. In an interview Wednesday with PBS, Mr. Obama said he had "no interest in any open-ended conflict in Syria."
Secretary of Defense Chuck Hagel reiterated, meanwhile, that if the U.S. was to take any military action against Syria, "it would be an international collaboration."
The British government of Prime Minister David Cameron has been building its own case for military intervention in Syria, and like the U.S. government, has claimed to have intelligence proving the attacks in Damascus' eastern Ghouta suburbs on Aug. 21 were the work of the Assad regime.
The U.K. Joint Intelligence Organisation released a report Thursday claiming "a limited but growing body of intelligence" showing that Assad's regime was guilty of the Ghouta gas attack. The report did not explain what that intelligence was.
The Obama administration is putting the finishing touches on two reports -- the first a classified assessment to be presented to Congress; the second, a declassified version for the American public -- meant to lay out the evidence that Assad's government used chemical weapons. But he faces questions from lawmakers about any planned strike.
"Having again determined your red line has been crossed, should a decisive response involve the use of the United States military, it is essential that you provide a clear, unambiguous explanation of how military action - which is a means, not a policy - will secure U.S. objectives and how it fits into your overall policy," House Speaker John Boehner wrote in a letter Wednesday.
"It is essential you address on what basis any use of force would be legally justified and how the justification comports with the exclusive authority of Congressional authorization under Article I of the Constitution," he continued.
The U.S. is also under pressure from the United Nations to refrain from striking Syria until a U.N. inspection team can finish its work to determining whether chemical weapons were used at all.
U.N. Secretary-General Ban Ki-moon said Thursday that U.N. experts will report to him as soon as they leave the country Saturday.
The team is expected to complete its inspection on Friday and their conclusions will be shared with members of the Security Council, Ban said. He didn't specify when that might be but said the experts "should be allowed to conclude their investigation activities."
His comments were in line with his previous calls for restraint in the face of increasing signs of retaliatory military action against Assad by the United States and its allies. Speaking to reporters, Ban said he repeated that message Wednesday in a conversation with President Obama.
"I expressed my sincere wish that this investigation team should be allowed to continue their work," he said after receiving an award in Vienna's City Hall and meeting Austrian government leaders.
"Diplomacy should be given a chance and peace given a chance," he said. "It is important that all differences of opinion should be solved through peaceful means and through dialogue."
But even after the inspections are concluded, a Security Council resolution authorizing force against Assad. Russia, a permanent member of the Council with veto power, has been a strong ally for Assad.
Indeed, Russian news service Interfax is citing military sources as saying Moscow is. Interfax says the moves are being made due to the "well-known situation" there -- referring to the Syria crisis. But a Russian government news service, Rianovosti, says the reassignments are part of a planned rotation and aren't linked with the situation in Syria.
The U.S. is also bolstering it's presence in the region. The USS Harry S Truman has arrived in the Arabian Sea and was scheduled to take the place of the USS Nimitz, which was supposed to head home. The Navy has ordered the Nimitz, which is in the Indian Ocean, to stay for now.
two submarines -- one American, one British -- are in the eastern Mediterranean along with four American destroyers and a fifth on the way -- all armed with cruise missiles. That's more than enough firepower for a strike Pentagon officials say would be limited to fewer than 50 targets.
Each of the destroyers carries about 40 cruise missiles - a satellite-guided weapon that carries a 1,000-pound warhead, has a range of 1000 miles or more and is accurate to within about 15 feet.
Retired Gen. Anthony Zinni, former CENTCOM commander, told "CBS This Morning" Thursday that the Russian maneuver were likely meant just to send a message.
"I think that's more just to send a signal or demonstrate their displeasure. It's not a threat in any way. We certainly have overwhelming force compared to them in the region and I don't think they're interested ... in interfering with us."
Meanwhile, prospects of a Western military strike and possible Syrian regime retaliation have sparked growing anxiety among civilians in Syria and neighboring countries.
In Damascus, some residents have begun stocking up on bottled water and canned food. Israelis have been standing in long lines to get government-issue gas masks. And the stream of Syrian refugees heading to Lebanon has picked up considerably in recent days.
Israeli police spokesman Micky Rosenfeld said officers were deployed to maintain order in the northern city of Haifa, where more than 5,000 people jostled in line as they waited for their protective kits. A sports arena there was being used as a distribution center to accommodate the crowds.
Israel's postal service, which oversees the distribution, said an angry mob forcibly took gas masks from a distribution center in Jerusalem on Wednesday, leading to the site's indefinite closure.
Israel has also called up reservists and deployed missile defense batteries in preparation for a possible Syrian response to an American attack.
Israel could also face a threat from Iran, a staunch supporter of Assad, in the event of a Western strike against Syria.
Mohammad Ali Jafari, leader of Iran's Islamic Revolutionary Guard Corps, said in a interview Wednesday with Tasnim news agency that Israel would face "imminent destruction" of strikes against Syria go forward, according to a Reuters report.