With Palestinians facing a dire shortage of bread, milk and other essentials, U.S. officials summoned Israeli and Palestinian negotiators to an emergency meeting Sunday to resolve a standoff over Gaza's main cargo crossing.

But the Palestinian's economic misery was liable to deepen as Hamas militants sworn to Israel's destruction prepared to formally present their new Cabinet to Palestinian President Mahmoud Abbas later in the day. The group's failure to bring moderate forces into its government is likely to strengthen Western resolve to cut off desperately needed aid.

Palestinian officials have accused Israel of closing the vital Karni cargo crossing for most of the past two months as retribution for Hamas' sweep of parliamentary elections in January.

Israeli officials deny the accusation, saying they have received numerous warnings that Palestinian militants are preparing to attack the site. Israeli also has offered an alternative crossing that the Palestinians reject.

Karni is the main gateway for goods entering and exiting Gaza. Under an agreement brokered by Secretary of State Condoleezza Rice in November, Israel and the Palestinians agreed to boost cargo traffic through the crossing. The accord was meant to give momentum to peace efforts and economic recovery programs after Israel's pullout from Gaza.

But the Karni deal was never implemented, and Israel has closed the crossing, citing security concerns.

The restrictions have hit Gaza hard. A U.N. statement issued Sunday said most bakeries in Gaza have closed due to grain shortages, and the area is suffering from an "extreme short supply" of dairy products and fruit. It also said the closure has hindered efforts to deliver emergency food supplies.

"We know that there is a developing problem of basic food goods, like wheat and other things," Abbas told reporters Sunday, saying he was sending a delegation to Tel Aviv to resolve the standoff. "This will be discussed today and for sure we will find solutions."

Stewart Tuttle, spokesman for the U.S. Embassy in Tel Aviv, said American officials called the meeting to address the Palestinians' urgent humanitarian concerns.

The meeting was scheduled at the residence of U.S. Ambassador Richard Jones, and senior officials from both sides were participating. Israeli defense officials confirmed their participation.

"The immediate concern is the humanitarian need in Gaza," Tuttle said.

During Karni's closure, Israel has offered to open an alternative crossing at Kerem Shalom, 25 miles south of Karni, to keep the flow of goods in and out of Gaza.

"We'd like Karni to be fully functioning as soon as possible ... The only reason Karni is closed is the definite terror warnings," Israeli Foreign Ministry spokesman Mark Regev said. "We don't understand why the Palestinians refuse to have the Kerem Shalom crossing open to bring in required and needed produce into Gaza."

The Palestinians reject the use of Kerem Shalom, saying it is not mentioned in the agreement Rice brokered and its capacity is far too small. They also complain that the crossing, located at the corner of the Israeli, Egyptian and Gaza borders, is entirely in Israeli territory and no sufficient link to Gaza has been established yet.

"This is unacceptable. The Karni crossing is the backbone of the Palestinian economy," Salim Abu Safiyeh, director of the Palestinian Border Authority, told Israel Radio.

Later Sunday, incoming Prime Minister Ismail Haniyeh was to present his proposed Cabinet to Abbas. Abbas told reporters he would review the names but would not decide immediately whether to accept the list. As president, he has the authority to demand changes.

Abbas, who favors negotiating a final peace settlement with Israel, has urged Hamas to moderate its violent ideology but likely will approve the Cabinet, his aides say. He will, however, warn Hamas that its refusal to soften its positions could hurt the Palestinians' international standing.

The United States and European Union have threatened to cut off hundreds of millions of dollars of aid to the Palestinians if Hamas does not renounce violence, recognize Israel and promise to honor existing peace agreements.

The group, which has killed hundreds of Israelis in suicide bombings, has rejected those conditions.

Haniyeh, a top Hamas official in Gaza, has not announced his Cabinet lineup. But Hamas officials say privately the group will keep the top three posts — foreign affairs, finance and interior, which oversees some security forces. Professionals will fill some of the other posts.

Abbas was elected separately last year to a four-year term and wields considerable authority. He cannot impose his own Cabinet lineup on Hamas, however, because it controls an absolute majority in the legislature.