For a man reputed to be Israel's biggest loudmouth, Avigdor Lieberman speaks softly. His flat, Russian-accented baritone rarely rises above a murmur. He's not a shouter. But when Lieberman talks, people listen — less because he is Israel's top diplomat than because of his knack for saying decidedly undiplomatic things. Lieberman believes that Israel's Arab citizens, who make up nearly 20% of the population, should be forced to sign oaths of loyalty. He has advocated the death penalty for Arab members of parliament who meet with members of Hamas. He calls the Obama Administration's push to curb the building of Jewish settlements in the West Bank a "mistake." It's not the kind of language you'd expect from a Foreign Minister, but Lieberman, 51, doesn't care. "I don't like political correctness," he says with a shrug. "I say exactly what I mean, and I mean what I say."

That bluntness has earned Lieberman the devotion of Israeli hawks and the disdain of liberals, Palestinians and just about every government in the Arab world. In February's election, Lieberman's 10-year-old party, Yisrael Beitenu (Israel Is Our Home), won the third highest number of seats in the Knesset, making him a linchpin of Prime Minister Benjamin Netanyahu's coalition government. That has complicated the Obama Administration's effort to pressure Israel to freeze settlement growth and restart peace negotiations with the Palestinians. How far Netanyahu travels in Obama's direction may depend on Lieberman's willingness to go along. "Lieberman is the most talented politician on the scene today," says Yaron Ezrahi, a professor of political science at Hebrew University of Jerusalem. "But his kind of politics is also dangerous — to Israeli democracy and to the prospect of any kind of peace settlement with the Palestinians."

The Foreign Minister is an unlikely firebrand. In person, he can be reserved to the point of shyness. When we met him at his office on June 24, we asked Lieberman whether Obama needed to take a tougher stand against Iran's crackdown on those protesting the results of the June 12 election. "This is a really fanatic, extremist regime that is still in power, and the young people ... are not getting any real support from the West," he said. "It shows the bad guys are winners." And he reiterated his resistance to any U.S. attempt to stop settlement growth. "We have our opinions, and the Americans have theirs," he said. "We can't suffocate our people."

Lieberman's hard line is the product of his past. His family moved to Israel in 1978 from the Soviet republic of Moldavia, now Moldova. His father fought in the Red Army in World War II but, like many other Soviet Jews, later spent years of forced exile in Siberia. "In my home, we spoke only about Israel," Lieberman says. "It was a dream that one day we would come here." Upon arriving, Lieberman enrolled at Hebrew University, moonlighting as a bouncer at a student nightclub and becoming active in the right-wing Likud Party. In the late '80s, he and his wife moved to Nokdim, a rugged West Bank settlement overlooking the Judaean desert, where he still lives. (Each night, he is driven home in an armored car, since portions of his commute pass by Palestinian villages.)

Around the time he settled in Nokdim, Lieberman met Netanyahu, then a rising Likud star. He ran Netanyahu's first, successful campaign for Prime Minister, in 1996, and became his chief of staff. "Netanyahu trusted him," says Tzahi Hanegbi, who served as the Justice Minister at the time. "He was quiet, discreet and loyal." In 1999, Lieberman split from Netanyahu and Likud, forming Yisrael Beitenu, an unapologetically nationalist party that drew its support from Israel's Russian-immigrant community. The party's most explosive position is the call for all citizens to pledge allegiance to the Jewish state as a condition of the right to vote — a barely veiled challenge to the loyalty of Israeli Arabs. "It's unacceptable that on Independence Day they are burning the Israeli flag," Lieberman says.

There's little chance the loyalty pledge will become law. Lieberman knows this. But by pressing the issue, he taps a growing impatience among Israelis with the country's Arab citizens, some of whom openly sided with Hamas during Israel's offensive against the militant group last winter. "His views have a constituency," says Hanegbi. "People want someone who will represent their fears and frustrations." Lieberman insists he supports an independent Palestinian state and says Israel is "ready to start negotiations without preconditions." But in Lieberman's view, peace doesn't mean cohabitation. "His governing idea is, Jews on one side, Arabs on the other," says a senior official.

It's an appealingly simple vision, but also a cynical one. Any final agreement between Arabs and Israelis will require them to share some territory — in Jerusalem, for instance — to which both can make rightful claims. Insisting on physical separation as a prerequisite for a peace deal is a safe way to ensure that one is never struck. Lieberman's views may be finding acceptance in the Israeli mainstream. But they are not the way to forge a lasting peace in the Middle East.