Prime Minister Ariel Sharon has postponed a trip this week to the United States, avoiding a meeting with President George W. Bush while Israeli forces remain in Palestinian areas in defiance of his call to leave.
After a day of relative quiet in the West Bank and Gaza, Israeli helicopters launched a pre-dawn missile attack on Palestinian security posts in northern Gaza.
The army said it attacked three Palestinian positions used to make mortars that militants fire at Jewish settlements.
A Palestinian security official said the buildings had been emptied of weapons a month ago.
"This is a continuous military escalation against our people. This means a new danger for the peace process that will lead to an increase in tension and lack of security", Mr Nabil Abu Rdainah, an aide to Palestinian leader Mr Yasser Arafat, said.
Mr Sharon's aides said the security situation meant he could not travel, and that he wants to be in the region to oversee an Israeli pullout from Palestinian areas it reoccupied last month.
Israeli cabinet ministers quoted Defence Minister Binyamin Ben-Eliezer as saying in the cabinet meeting today that forces could begin to withdraw from the West Bank town of Qalqilya later in the day.
The US administration is concerned that Israel's military advances into Palestinian-ruled areas could undermine Arab and Muslim backing of Washington's campaign against Islamic militant Osama bin Laden.