JERUSALEM  When Hamas blew large holes in Gaza’s border with Egypt, allowing thousands of Palestinians a chance to stock up on medicines, food and consumer goods, it also blew a large hole in the Israeli policy, backed by Washington, of squeezing the population of Gaza in the hope that they would turn actively against Hamas.

As Israeli leaders pushed Egypt to close the border and fumbled for an effective response, the apparent Hamas success put Egypt into a bind and further undermined the chances that Prime Minister Ehud Olmert of Israel and President Mahmoud Abbas of the Palestinian Fatah faction could succeed in negotiating a peace treaty  let alone by the time President Bush leaves office.

Early efforts by Egypt on Friday to reseal the border failed when Hamas broke through more areas of the border wall with bulldozers, and Palestinians continued to move easily into Egypt on Saturday, sometimes with cars and trucks.

The confrontational tactics of Hamas, the Palestinian branch of Egypt’s opposition and banned Muslim Brotherhood, also presented a difficult quandary for President Hosni Mubarak of Egypt. The plight of the Palestinians, especially those in Gaza, is a deeply emotional issue for Egyptians and other Arabs, an issue often promoted and sometimes manipulated by Arab leaders and Arabic satellite channels like Al Jazeera.