Israel's hard-line foreign minister said Monday that his party will try to block any extension of Israel's settlement slowdown, a move that could derail the recently launched Mideast peace negotiations.

Avigdor Lieberman said the Israeli government must keep its promise to voters that the 10-month slowdown, declared last November under U.S. pressure in order to draw the Palestinians to the negotiating table, will end as scheduled at the end of the month.

The Sept. 26 deadline is a challenge for the fragile talks launched in Washington last week. The Palestinians say they will quit the talks if settlement construction accelerates, but not ending the slowdown could potentially bring down the Israeli government. Prime Minister Benjamin Netanyahu has yet to say how he will handle the deadline.

"A promise is a promise," Lieberman told Israel Radio. "We will not agree to any extension."

"I promise that if there's a proposal that we don't accept it will not pass," he added.

Lieberman's Yisrael Beitenu party is a key member of Israel's governing coalition, which is led by Netanyahu's Likud party.

It holds 15 seats in parliament, making it the second-largest member of the coalition and giving it the ability to rob the government of its parliamentary majority if it pulls out. Other coalition partners, and members of Netanyahu's own party, also favor resuming construction.

In a sign that compromise was possible, however, Lieberman told the daily Yediot Ahronot that he would not quit the coalition even if he does not get his way.

"We will not leave or bring down the government. We will fight from the inside for what we believe," he told the paper.

At the summit marking the relaunch of peace talks in Washington last week, Netanyahu used unusually warm language about the Palestinian leadership and the chances for peace. But the Israeli foreign minister has been vocal in his pessimism.

Speaking to diplomats in Jerusalem on Monday, Lieberman said the stated goal of the talks — a peace agreement within one year — was unrealistic.

The Israeli government says construction in settlements continued during previous rounds of peace talks, and that building does not compromise a future deal.

Lieberman's party ran on a platform that questioned the loyalty of Israel's one-fifth Arab minority, and Lieberman, known for blunt and often unpredictable language, is perhaps Israel's most polarizing politician. A resident of a West Bank settlement himself, he has absented himself from active involvement in the peace talks, which are being conducted by Netanyahu's office.

Vice Prime Minister Silvan Shalom, a prominent member of Netanyahu's party, said extending the slowdown would pose a "huge danger" to the coalition.

"Within the coalition, there is a huge majority against it," Shalom told reporters late Sunday. He said the issue could only be resolved through negotiations.

Netanyahu is seeking a way to get through the Sept. 26 deadline without dismantling his coalition, alienating the Palestinians or angering the U.S. administration, which is backing the talks and has invested time and political capital in their success.

Netanyahu is slated to meet Palestinian President Mahmoud Abbas for a second round of talks next week in Egypt and Jerusalem. U.S. Secretary of State Hillary Clinton is also scheduled to attend.

About 300,000 Israelis live in West Bank settlements, among the territory's some 2.5 million Palestinians. In addition, almost 200,000 Israelis live in east Jerusalem, the section of the holy city claimed by the Palestinians.

The Palestinians and the international community say the settlements are obstacles to peace because they eat up land the Palestinians want for a future state.

The slowdown has cut the construction in the settlements, though the extent of the drop is the subject of disagreement.

According to official government statistics released last week, a total of only five new building projects were begun in settlements in the first half of 2010, compared to 673 in the first half of 2009.

Israeli advocacy groups tracking settlement construction dispute those numbers.

The group Peace Now says building has begun on around 450 new housing units since the slowdown went into effect last November, around 300 of them in violation of the terms of the freeze. Peace Now says those numbers mark a drop of about 50 percent in new projects.

Settlement expert Dror Etkes said government statistics show the number of units under construction overall in the first quarter of this year was 2,517, a drop of only 15 percent compared to the last quarter of 2009.

Groups critical of settlement building say if the slowdown is revoked now it will have had nearly no effect on settlement construction in the long term.