Prime Minister Ariel Sharon again confirmed that Israel would not ease restrictions before Palestinian parliamentary elections in January as long as Hamas, a militant group that has killed hundreds of Israelis, is allowed to participate.
The threat, if carried out, could make it nearly impossible for Palestinians to conduct the poll, and Palestinian officials strongly condemned Sharon's statement as meddling in their internal affairs.
The Palestinians say Israeli roadblocks throughout the West Bank must be lifted ahead of the Jan. 25 election so candidates can campaign freely and voters can travel to rallies and the polls.
US President, however, warned Abbas that violent Palestinian groups could undermine the nascent Palestinian democracy.
On Sunday, Sharon repeated his long-standing demand that Abbas disarm all Palestinian militant groups.
"Israel's position is that it will not be able to cooperate with the elections if Hamas in its current form takes part," a government statement quoted Sharon as telling his Cabinet. "There cannot be a situation where an armed organization ... can take part in elections."
Abbas has repeatedly refused to disarm the popular militant group, saying that such a confrontation could lead to civil war. Instead, he has brokered a shaky truce agreement with militants not to attack Israel and has worked to bring them into Palestinian political life by having them field parliamentary candidates.
Hamas, which opposes the existence of the Jewish state, has carried out dozens of suicide bombing attacks against Israelis during the past five years. Palestinian officials hope Hamas' involvement in politics will moderate the group.
The Islamic group participated in three rounds of local elections, but the vote in January would be the first time Hamas would participate in a parliamentary vote.
Palestinian negotiator Saeb Erekat called Sharon's threat "a very, very dangerous development."
"In my opinion, the Palestinians today have a rare opportunity to make progress with the (peace) process ... but there is one area where I will not make any concessions and that is the issue of security," Ariel Sharon said.
Also Sunday, Israeli security officials said Defense Minister Shaul Mofaz hoped to reopen the Rafah border crossing - the Gaza Strip's main gateway to the outside world - within two weeks.
Israel closed the crossing, located along the Egyptian border, shortly before it withdrew from Gaza in September, saying it would stay shut for six months to allow for new security and customs arrangements. But Palestinians and international mediators have pressured Israel to open it quickly.
Also Sunday, a 12-year-old Palestinian boy shot dead by Israeli troops while playing with a toy gun was buried in the West Bank town of Jenin. His family donated his organs for transplant, and his heart, liver and lungs were transplanted into the bodies of three Israeli children, the AP reports.