Meanwhile, Israeli troops massed Saturday outside Gaza as Hamas militants in the volatile coastal strip launched volleys of mortar shells and homemade rockets at Israeli targets for the third straight day.
An Israeli raid into Gaza would make it far more difficult to re-establish the five-month truce and could lead to a breakdown in coordination between the two sides just a month before Israel begins its planned withdrawal from the Gaza Strip.
Palestinian officials have said they would prevent attacks against Israeli forces by militants ? who are eager to prove they are pushing Israel out of Gaza ? during the pullout scheduled for mid-August. But their failure to stop the mortar and rocket attacks raised questions about their ability to keep that promise.
Speaking from his Gaza City office in an address on Palestinian television Saturday night, Abbas said the cease-fire agreement was in the best interest of the Palestinians.
"I call upon all the Palestinian factions and forces to renew and to declare their commitment to what we had agreed upon, to respect the (Palestinian) Authority ... and to obey the truce," he said. "We are not going to allow anyone to gamble with our national cause."
Hamas spokesman Musher al Masri said the attacks on Israel were an effort to "prove to the enemy that Palestinian blood is not cheap." He did not say whether Hamas would return to the cease-fire.
In response to the growing violence, Egypt decided to send Mustafa Behairy, a top intelligence official, to Gaza on Sunday to meet with Abbas and Hamas leaders in an effort to restore calm, according to Egyptian officials who spoke on condition of anonymity for fear of damaging the mediation effort.
Secretary of State Condoleezza Rice also changed her schedule to include a last-minute trip to the region, expected to be next week.
As part of its crackdown on militants following a Palestinian suicide bombing and fatal rocket attack that killed a total of six Israelis, Israel arrested more than 30 wanted men early Saturday in the West Bank cities of Hebron, Bethlehem, Nablus and Tulkarem, the army said. Israel also continued to prevent Palestinians from crossing into Israel from the West Bank and the Gaza Strip.
"Israel will not forfeit its basic right to self defense, especially in the face of a continued and persistent Palestinian refusal to prevent terrorist attacks against Israel," said David Baker, an official in Israeli Prime Minister Ariel Sharon's office.
On Friday, Israel resumed the targeted killings of militants, which had been suspended under the truce, killing seven Hamas militants in air strikes and a follow-up raid in Gaza and the West Bank. Another Palestinian was shot and killed by soldiers after he threw stones at them, hospital officials said.
Abbas blamed Israel for the recent outbreak of violence.
"We hold the Israeli government fully responsible for the consequences of its policy, which reflects a step backward from what we had achieved ... and sabotaged any chance to maintain the truce," he said. "No one could expect the continuation of the truce from one side."
Militants launched new mortar and rocket barrages at Gaza settlements and nearby communities in Israel on Saturday, slightly injuring two people in the northern Gaza settlement of Nissanit, officials said.
Sderot, an Israeli town outside Gaza, was also hit repeatedly.
"It looks like a war here," Sderot Mayor Eli Moyal told Israel Radio. "It is impossible to continue living this way. This is unbearable."
"If this is what happens before disengagement, God knows what will be here next month," he said.
Amos Gilad, a top Defense Department official, defended Israel's resumption of targeted killings, saying they were intended to prevent imminent attacks.
"Israel's policy is not to allow 'ticking bombs' to reach their targets," he told Israel Radio. "Every pinpoint attack saves lives."