REUTERS - Israel reopened its border crossings with the Hamas-controlled Gaza Strip on Friday, a day after Prime Minister Ehud Olmert indicated the Jewish state was preparing for a possible offensive into the coastal territory.

Palestinian workers at the crossings said a limited amount of fuel had arrived for the Gaza Strip's main power plant and trucks loaded with grain had crossed into the impoverished enclave.

Olmert urged Palestinians in the Gaza Strip on Thursday to reject their Hamas rulers and stop rocket fire at Israel and threatened to use force if they did not -- a clear indication that Israel was preparing a possible Gaza offensive.

Israeli Defence Minister Ehud Barak said he ordered the crossings to be opened to allow in "essential humanitarian" supplies after receiving numerous requests from the international community.

Israel tightened its blockade on the Gaza Strip after Hamas Islamists routed rival Fatah forces to seize the territory in June 2007.