Israel should present Palestinian Authority President Mahmoud Abbas with an ultimatum, Foreign Minister Avigdor Lieberman said this weekend: If he doesn't resume negotiations and abandon his unilateral campaign for UN recognition as a state, Israel will cease to see him as a legitimate negotiating partner.

In an interview with Haaretz, Lieberman said the resumption of the UN campaign was the main reason for the letter he sent last week to the foreign ministers of members of the Middle East Quartet (which comprises the United States, United Nations, European Union and Russia). In that letter, he urged them to work to replace Abbas by pressuring the PA to hold its long-overdue presidential election.

Last year, Abbas asked the United Nations to admit Palestine as a full member state. But that bid failed, as the Palestinians were unable to secure the necessary support from nine of the Security Council's 15 members.

This year, Abbas plans to ask the General Assembly to recognize Palestine in the 1967 lines as a nonmember observer state. In the General Assembly, the Palestinians have an automatic majority; he can count on the support of at least 130 countries. And though General Assembly decisions are nonbinding, such a decision would enable the Palestinians to join the International Criminal Court and seek to indict Israel for alleged war crimes in the West Bank and Gaza Strip.

"Everyone is asking 'why now?' Why did I suddenly send that letter?" Lieberman said. "I did it because Abu Mazen [Abbas] is playing for time until November with his UN move. He'll come to the UN in September and deliver a vicious speech against Israel, but he'll seek a vote only in November after the U.S. elections. He doesn't want to embarrass the Americans before the elections, and he won't rupture relations with [U.S. President Barack] Obama."

The PA sent a harshly-worded letter of complaint to Prime Minister Benjamin Netanyahu this weekend, demanding that the Israeli government state unequivocally whether Lieberman's letter represents its position.

Lieberman told Haaretz that over the last three years, Israel hasn't once taken the initiative on the Palestinian issue; it has only reacted to Palestinian, American or European moves. "Our policy was to preserve the quiet at any cost," he said. "But it can't last forever; in the end, it will blow up."

Israel, he said, must use the time remaining until November to take various steps to thwart Abbas' UN application. He suggested that the cabinet adopt a new policy toward the Palestinians.

"The cabinet must make a decision that will make clear to Abu Mazen that 'If you don't return to the negotiating table, and if you continue your UN move, then from our perspective, you will no longer be a partner, and we won't talk to you.'"

He also said Israel should open a delegitimization campaign against Abbas. "We must not sit and wait until November, and only then put out the fire, as we always do," he said. "Abu Mazen is waging diplomatic terror against us a campaign of delegitimization against Israel by encouraging boycotts, overseas lawsuits and incitement. We must do the same to him. By November 7," the day after the U.S. elections, "we must make Abu Mazen illegitimate in the eyes of the world."

Lieberman said his call for new elections in the PA wasn't an attempt to intervene in the PA's internal politics, but an attempt to make clear to the world that Abbas is still in power despite his term of office having expired long ago, and thus has no public legitimacy.

"We've seen that betting on Middle East dictators doesn't help anyone," he said. "Abu Mazen, too, will eventually be ousted."

To block the Palestinians' UN bid, Lieberman said, Israel must impose heavy diplomatic and economic sanctions on Abbas.

"We have enough leverage to make him feel it isn't worthwhile to do this," he said. "For once, we need to use it, and not just threaten."