Israel on Sunday barred the delegations of five countries from attending a diplomatic conference in Ramallah, in the West Bank, upending plans by the Palestinian president to announce his intention to renew the Palestinians’ bid this September for enhanced status in the United Nations.

A senior Israeli official said the delegations — from Algeria, Bangladesh, Cuba, Indonesia and Malaysia — were denied permission to use Israeli border crossings because their governments do not recognize the state of Israel. Palestinian officials said the delegations had planned to enter on a helicopter from Jordan, and called the decision “childish,” “crude,” “irresponsible” and “blackmail,” saying it symbolized the larger problem with Israel’s occupation of the West Bank territories it seized in 1967.

“Israel is really trying to not just lay a physical siege but also a political siege,” said Hanan Ashrawi, a member of the executive committee of the Palestine Liberation Organization. “We need to be able to move, to breathe, to act as a member of the community of nations. We cannot constantly be under the boot.”

The 5 countries were among 12 so-called nonaligned nations sending delegations to Ramallah for an emergency conference on the Palestinian issue. The other seven — Colombia, Egypt, India, Senegal, South Africa, Zambia and Zimbabwe — declined to attend without their comrades. The 12 were expected to approve a “Ramallah Declaration,” which condemns Jewish settlement in the West Bank and supports the Palestinians’ bid to upgrade their status at the United Nations.

The 12 countries are among more than 100 that are not aligned with a particular power bloc. The meeting would have been the first of its kind in the West Bank since the establishment of the Palestinian Authority.

Riad al-Malki, the Palestinian foreign minister, said Saturday that President Mahmoud Abbas of the Palestinian Authority would use his Sept. 27 speech at the United Nations to make his case for observer-state status, but would not ask the General Assembly to vote on the matter until late November. Last year, the United States vowed to veto Mr. Abbas’s statehood bid in the United Nations Security Council, and it has pressured Palestinian officials not to force the issue again before the American presidential election.

Unlike the Security Council, where the issue died in a deadlocked committee vote last year, the General Assembly is virtually guaranteed to support the Palestinians’ request, with perhaps 130 of its 193 members voting in favor of it. Observer-state status, akin to the Vatican’s status, is less than what the Palestinians requested from the Security Council, but would allow them access to institutions like the International Criminal Court, where they could, for example, pursue legal cases against Israeli settlers and officials for actions in the West Bank.

A senior Palestinian official, speaking on the condition of anonymity because he was not authorized to discuss the internal deliberations, said that the timing of the request would not be decided until after a Sept. 5 meeting of Arab nations, but that one leading possibility was to ask for a vote on Nov. 29, the 65th anniversary of the United Nations vote to partition the territory of Palestine into Jewish and Arab states. “Many diplomats have said it would be very difficult for their country on the 29th of November not to vote in favor,” the official said.

Khalil Shikaki, a Ramallah pollster and political analyst, said that public support among Palestinians for a United Nations bid had dropped to 73 percent in June from 83 percent last September, but that it still significantly outweighed enthusiasm for other options, like a unilateral declaration of statehood; nonviolent or violent resistance; and a dissolution of the Palestinian Authority.

“He is doing it because he is running out of other options,” Mr. Shikaki said of Mr. Abbas. “It will certainly give him greater legitimacy at home.”

The timing “gives him a little bit of bargaining power,” he added. After the November election, the American president will have “greater flexibility” to “begin a dialogue with Abbas, and Abbas can say, ‘O.K., I’m willing to postpone the vote if you give me a better option.’ ”

But Israel and the United States have both denounced the Palestinians’ decision to choose a United Nations path, saying that only direct negotiations can resolve the long-running conflict. An internal Palestinian document about the United Nations bid outlines a host of possible negative responses, including a freeze of United States aid to the Palestinian Authority and closing the P.L.O.’s diplomatic mission in Washington.

Israel, the document says, might seize Palestinian taxes it collects; further restrict the movements of Palestinians; suspend building permits in the parts of the West Bank under Israeli control; and take steps toward a unilateral withdrawal, essentially pre-defining the borders of a future Palestinian state.

The senior Israeli official, also speaking on the condition of anonymity because he was not authorized to do otherwise, said Israel saw the renewed United Nations action as a particular slap after several recent gestures, including the release of Palestinian bodies buried in Israel; the signing of a tax agreement with the Palestinian Authority; the advance of aid to ensure salaries were paid before Ramadan; and an agreement to develop a gas field off the Gaza shore.

“All this shows how much can be gained through dialogue, through discussion, through engagement,” he said. Returning to the United Nations is “the opposition of engagement, that’s going unilaterally,” he added. “I don’t see what good can come from this.”

The cancellation of the Ramallah conference came as an Israeli airstrike killed a Palestinian militant and seriously wounded another in the southern Gaza Strip town of Rafah.

The strike on a motorcycle, which came after two months of relative calm, killed Eid Oukal, 22, and wounded Ahmed Sai’d Isma’i, members of the Popular Resistance Committees, a militant group loyal to the Hamas movement, which governs Gaza, and also said to have ties to a separate group, the Tawhid and Jihad organization.

A statement by the Israeli Defense Force said that Mr. Isma’i was “among those responsible” for killing an Israeli construction worker along the Egypt border in June, and that both men were planning a terrorist attack against Israeli civilians on the border.

Late Sunday, two rockets fired from Gaza exploded in southern Israel, according to Agence France-Presse, but a military spokesman said they caused no casualties or damage.