The United States cast the first U.N. Security Council veto in nearly two years Thursday, blocking an Arab-backed resolution that would have demanded Israel halt its military offensive in the Gaza Strip.

The draft, sponsored by Qatar, accused Israel of a "disproportionate use of force" that endangered Palestinian civilians, and it demanded Israel withdraw its troops from Gaza.

Earlier Thursday, U.N. Secretary-General Kofi Annan announced he will send three veteran U.N. officials to the Middle East in a bid to defuse what he called a "major crisis" there, the United Nations said Thursday, as the European Union criticized Israel for using what it called "disproportionate" force in its attacks on Lebanon.

Annan was responding to a flare-up in violence that began two weeks ago when Israeli forces launched an offensive in the Gaza Strip to free a captured soldier. Israel then launched attacks against Lebanon on Wednesday after Hezbollah militants captured two Israeli soldiers.

The team will be led by Vijay Nambiar, Annan's special political adviser. It also includes U.N. Mideast envoy Alvaro de Soto and Terje Roed-Larsen, Annan's special envoy who has overseen implementation of a U.N. resolution demanding Syria end its sway over Lebanon.

The EU also called Israel's naval blockade cutting off supply routes to Lebanon unjustified.

"The European Union is greatly concerned about the disproportionate use of force by Israel in Lebanon in response to attacks by Hezbollah on Israel," according to a statement issued by Finland, which holds the EU's rotating presidency. "The presidency deplores the loss of civilian lives and the destruction of civilian infrastructure. The imposition of an air and sea blockade on Lebanon cannot be justified."

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In the EU's strongest comment on the escalating violence, the statement said "actions, which are contrary to international humanitarian law, can only aggravate the vicious circle of violence and retribution, and cannot serve anyone's legitimate security interests."

It called for the immediate release of the Israeli soldiers, and urged "all countries in the region to work for the restoration of calm in order to avoid the further escalation of the situation into war."

Separately, EU foreign policy chief Javier Solana said he was planning a peace mission to the Middle East. Solana said he was in "permanent contact" with players in the region and with Annan.

"Following these contacts, I envisage going to the region," he said in a statement.

EU diplomats said it was unclear when Solana would leave, but it could be before Monday's meeting of European foreign ministers in Brussels which will likely be dominated by the Middle East crisis.

The EU called on all sides to halt the escalating violence and take care to avoid more civilian casualties. EU spokeswoman Emma Udwin said EU foreign ministers could discuss whether the Israeli military attacks on Lebanon were compatible with the bloc's trade and cooperation agreement with Israel, which is conditional on respect for international law.

"I'm not a lawyer, but that will be a subject of a major discussion that foreign affairs ministers will conduct on Monday. There, the EU's reaction will take form and will be explained in some detail," she told reporters.

She stressed, however, that the EU recognized "Israel's right to defend itself." Israel's military action came after a cross-border raid by Hezbollah guerillas in which two Israeli soldiers were captured and several others were killed.

EU diplomats said there was no suggestion the EU would consider freezing any part of the agreements regulating economic relations between Israel and the 25-nation EU — Israel's main trading partner which buys about one-third of Israel's exports.

"Every effort must be taken not to harm civilians," Udwin said. "All parties must respect their obligations under international law to protect civilians from the effects of conflict."