Israel is sending food into the Hamas-ruled Gaza Strip while threatening an invasion. But Hamas is not backing down.

Israel reopened border crossings and sent basic food and supplies into Gaza. The army said 90 trucks crossed the border carrying rice, flour, fuel and medicine. The border crossings have been closed since a six-month Gaza cease-fire expired a week ago. Since then, Palestinian militants have bombarded southern Israel with dozens of rockets and mortar shells.

The crossings were opened a day after Israeli Prime Minister Ehud Olmert threatened to invade Gaza, which is ruled by the Islamic militant group Hamas. Olmert issued the threat in a rare interview on al-Arabiya television, which broadcasts to the Arab world.

"We have enormous power, we can do things which will be devastating," he said. "And I keep restraining myself and I keep restraining my friends all the time and I tell them, 'Let's wait, let's wait, let's wait. Let's give them another chance.'"

But with rockets and mortars terrorizing southern Israeli towns and farming communities, Mr. Olmert has come under increasing pressure to act against Hamas, a group that refuses to renounce violence or recognize Israel. The prime minister says he is running out of patience.

"And I'm telling them now, 'It may be the last minute.' I'm telling them, 'Stop it, we are stronger. There will be more blood there.' Who wants it? We don't want it," he said.

Israel is reluctant to invade Gaza, fearing high casualties among Israeli soldiers and Palestinian civilians, and in turn, international condemnation.

That could be why Hamas seems unfazed by the Israeli threats.

Hamas spokesman Ismail Radwan said Gaza's ground is not covered with fragrant flowers, but with men and women suicide bombers. He said Israel would not dare invade Gaza because it knows it would pay a heavy price.