JERUSALEM — Israel announced Wednesday that it would lift its air and sea blockade of Lebanon this evening, three weeks after the cessation of hostilities, because international forces were ready to move into place to impose an arms embargo on the Hezbollah militia.

Prime Minister Ehud Olmert said that Israel would yield its "control positions over Lebanon's seaports and airports" to international supervision.

French, Greek, British and Italian ships will patrol Lebanon's coast until German ships arrive in two weeks. German monitors will also help patrol Lebanon's airport to prevent the resupply of rockets, launchers and heavy weapons to Hezbollah from its main supporters, Syria and Iran.

Preventing weapons from moving across the land border from Syria remains the main issue. A senior Israeli official who spoke on the condition of anonymity because he was not authorized to talk about the subject, said Israel had "an understanding" that international forces would deploy alongside the Lebanese army to monitor that border.

But Miri Eisin, a spokeswoman for Olmert, said the land border "is still an open issue — it's not resolved so far as Israel is concerned." Olmert wants Lebanese forces with U.N. forces at each of the nine crossing points along the mountainous 205-mile border with Syria, Eisin said. While the border is unfenced and largely unmarked, large rockets and truck-based launchers cannot be brought over land by donkeys, she said, so the crossings are crucial.

"The land border with Syria is the wild card and the real test of the arms embargo," said the spokesman for the Israeli Foreign Ministry, Mark Regev. "We're hopeful we'll see Lebanese forces augmented by international forces there on the border enforcing the arms embargo. It would be very nice to believe Syria would change its policies, but we'd like a verification process."

Israeli military officials have said that if they have evidence of continuing supplies of rockets and launchers to Hezbollah on trucks from Syria, Israel will feel justified in bombing those trucks.

Israel has been pressed hard to lift its air and sea embargos by the U.N. secretary general, Kofi Annan, who had suggested it might be lifted within 48 hours.

In Cairo, Egypt, the Lebanese foreign minister, Fawzi Salloukh, said that Lebanon "would wait for the 48 hours given by Kofi Annan, and if the situation is resolved, we will thank him."

"If it is not," Salloukh added, "the Lebanese government will take the necessary measures and break the blockade with all our might."

Annan, on his arrival in Madrid, Spain, on Wednesday at the end of his Middle East tour, said he had worked on the plan during his flight from Turkey and was pleased with the results. "The lifting of the blockade will enable Lebanese Prime Minister Fouad Siniora and his government to accelerate their economic recovery and reconstruction program," he said in a statement.

Israel is depending on Lebanon to help bring about the return of two soldiers captured by Hezbollah on July 12; those seizures led to the war. And with various Arab airlines vowing to land in Beirut anyway, Israel clearly decided that it was time to lift its restrictions. Israel has already granted permission for most civilian aircraft and aid shipments to land in recent days.

"We have to play our cards right and know when we have enough," said the senior Israeli official. "It's the big stuff, the larger rockets and launchers, that we have to worry about."

European navies will monitor the seacoast, and the airport itself is a relatively small area that will be easy to monitor, the official said. As for the difficult issue of the Syrian border, "we have an understanding" that international forces will be there to help Lebanese forces, the official said, even though the Syrian government had warned Lebanon that any international presence on its border would cause Syria to close the border.

Under the resolution that ended the fighting, the Lebanese government must request the help of the U.N. force to monitor the border, and the Israeli official insisted that Israel had been told that Lebanon would make the request.

Annan has met with all sides in an effort to push along efforts to carry out the Security Council resolution, 1701, which went into effect on Aug. 14 and largely stopped the fighting. He has said he will appoint a special envoy to work on the return of the Israeli soldiers captured by Hezbollah, presumably in exchange for a few Lebanese prisoners held by Israel for years, and for Hezbollah fighters captured during the war.

Annan has pressed European nations, and nations like Turkey and Indonesia with large Muslim populations, to provide troops for the expanded U.N. force.

About 3,250 international troops are now in Lebanon, but Annan expects the figure to reach 5,000 by the end of next week. The resolution calls for a maximum of 15,000 troops, but a senior European diplomat, who spoke on the condition of customary diplomatic anonymity, said that even 12,000 would be "a good showing."

Elsewhere, in Gaza, some staff members from the Palestinian prime minister's office joined a strike by civil servants demanding salaries from the Hamas government, which has been unable to pay them in full for six months.

The strikes have been pressed by Fatah, Hamas' political rival, but also reflect popular unhappiness with the inability of the Hamas government to secure enough funds, in the face of a Western aid cutoff and an Israeli refusal to hand over tax and customs receipts, to pay 165,000 civil servants more than small, intermittent stipends.

Israel, the United State, and Europe want Hamas to recognize the right of Israel to exist, forswear violence, and recognize previous Israeli-Palestinian agreements. Some Europeans are now suggesting, according to a senior French diplomat, that those restrictions be eased if the Palestinians come up with a national-unity government that at least forswears violence and terrorism. The United States and Britain are against weakening the terms demanded of Hamas.