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The U.S. is proposing deploying international observers at the main cargo crossing between Israel and Gaza to prevent repeated security closures of Gaza's economic lifeline, a Palestinian negotiator said Monday.

The Palestinians support the idea, and Israel is studying it, officials said.

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The Karni crossing has been closed by Israel for long stretches this year following security alerts and attacks by Palestinian militants. Virtually all of Gaza's imports and exports go through Karni.

Palestinian negotiator Saeb Erekat said the proposal to deploy international observers on the Palestinian side of the crossing came from Maj. Gen. Keith Dayton, the U.S. security coordinator in the West Bank and Gaza. The plan also calls for the training of Palestinian security officials and building a new terminal at Karni, Erekat said.

The Israeli daily Haaretz said 90 international observers would be deployed on the Palestinian side of Karni. The U.S. Embassy declined immediate comment.

Erekat said the proposal has been approved by Palestinian President Mahmoud Abbas and now awaits Israeli approval. Israeli officials said they were studying the idea.

Also Monday, four Palestinians were killed near Gaza City. Palestinian security officials said the four were manning roadblocks in the area when they were hit by an Israeli missile fired from the air. The Israeli military said Israeli soldiers operating in the area killed three Palestinians in a firefight, but did not know of a fourth man killed.

Two of the dead were from Hamas and two from the presidential guards linked to President Mahmoud Abbas' Fatah movement, Palestinian security officials said.

In southern Gaza, Hamas gunmen shot a motorist who refused to stop at a roadblock, witnesses said. The gunmen said they came under fire from the approaching car and returned fire. The identity of the dead man was not immediately known.

However, there have been growing tensions between Hamas and Abbas' rival Fatah movement in recent months, with gunmen from both groups often engaging in street clashes.

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The growing chaos and lawlessness in Gaza prompted an unusually frank comment by the spokesman of the Hamas government, Ghazi Hamad, who wrote that the Palestinians have bungled the aftermath of Israel's withdrawal from Gaza and should stop blaming Israel for all their woes.

The article, a rare case of self-criticism, was published in Palestinian newspapers Monday. Hamad said it expressed his personal opinion and did not represent the position of the government.

Hamad urged Palestinians to look beyond the conflict with Israel in searching for the causes of internal violence and lawlessness sweeping through the Gaza Strip.

"I am not interested in discussing the ugliness and brutality of the occupation because it is not a secret. Instead, I prefer self-criticism and self-evaluation," Hamad wrote.

Israel's withdrawal from Gaza last year, after 38 years of occupation, had raised hopes the Palestinians would rebuild the impoverished coastal strip as the first step toward gaining full independence in Gaza and the West Bank.

However, rival Palestinian factions have been locked in a violent power struggle, and fighting with Israel has continued.

"Our extreme joy at their departure made us forget the most important question: What is our next step?" Hamad wrote. "We heard that a promising future was waiting for us and for Gaza — and so we were optimistic that the blood of our martyrs and injured and the suffering of the entire country hadn't been in vain."

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