JERUSALEM — This week, Foreign Minister Avigdor Lieberman of Israel gave a dinner for the foreign ministers of France and Spain, who were here urging a West Bank settlement freeze to improve the chance for peace with the Palestinians. When the meal was over, Mr. Lieberman spoke.

“I don’t expect you to solve the world’s problems,” he told his guests, Bernard Kouchner and Miguel Moratinos. “But I do expect you at least to solve problems in Europe before you come to teach us how to resolve our conflicts. After you solve the Caucasus, Cyprus, Serbia and Kosovo, come to us, and then I will be ready to accept your advice.”

The event was private, but Mr. Lieberman’s spokesman called Israeli journalists and read them the text of what the minister had said.

It was in many ways typical of Mr. Lieberman, an abrasive nationalist who said when he took office 18 months ago that he was more interested in straight talk than diplomacy. Still, along with his speech at the United Nations last month, which dismissed peace with the Palestinians as “decades” away, at best, it signaled a ratcheting up of his challenge to Prime Minister Benjamin Netanyahu. Their rivalry is shaping Israeli policy at a delicate diplomatic moment.

“Lieberman’s big dream, which is Netanyahu’s big nightmare, is that he will become leader of the Israeli right,” Einat Wilf, a Labor Party member of Parliament, said in a telephone interview. “The more Netanyahu edges to the center and talks about peace, the more a big space opens up for Lieberman.”

The choice of Mr. Lieberman as Israel’s foreign minister was a surprising one to begin with. But it had a rationale. For him, it was an opportunity to develop credentials as a statesman. For Mr. Netanyahu, the hope was partly that Mr. Lieberman’s brawling political habits might be tamed in the world of striped trousers.

For a while, it seemed to work. On his first trip as foreign minister in May 2009, Mr. Lieberman spoke about improving relations between Israel and Europe and promised that Mr. Netanyahu would “reach a secure and definitive peace with the Palestinians and the Arab nations around us.” Last November, Mr. Lieberman, himself a West Bank settler and leader of the ultranationalist Yisrael Beiteinu party, joined his cabinet colleagues and approved a 10-month settlement moratorium in the West Bank.

But lately a change in his public manner has become evident. Close observers attribute it to a number of things.

The most important may be that the left/right divide in Israel falls increasingly today along the question of how Israel views its place in the world. The left and center want to combat the country’s isolation; the right says the issue is overstated and not a reason to shift policy from key interests like holding onto East Jerusalem and parts of the West Bank. That is Mr. Lieberman’s view, and he is using an office usually associated with internationalism for a strong domestic political goal.

But other matters play a role. The police have recommended that he be indicted on fraud charges from an earlier business, and if he feels he has to quit, he probably wants to go out on a populist wave.

In addition, he is being kept away from the core of Israel’s foreign affairs — relations with Washington and the Arabs — which are handled by Mr. Netanyahu and Ehud Barak, the defense minister from Labor.

To some extent, this was Mr. Lieberman’s wish. He is a skeptic about the Palestinians and told his colleagues upon arrival at the ministry that he saw their real role as building relations in Asia, Africa and former Soviet states.

Born in Moldova and a native speaker of Russian, Mr. Lieberman, 52, moved to Israel at age 20. His style may stem from a feeling of still being an outsider. When he became foreign minister, he said he would concentrate on areas neglected by the traditional foreign policy elite.

But he also started to resent being sidelined. When, for example, relations with Turkey reached a crisis level after nine people died in May in Israel’s raid on a Turkish flotilla, Mr. Netanyahu sent Trade Minister Benjamin Ben-Eliezer to see Turkey’s foreign minister without telling Mr. Lieberman, who did not hide his anger.

In addition, under American pressure, Mr. Netanyahu started to talk more about peace with the Palestinians. He declared his goal to be an agreement in a year, he called the Palestinian president, Mahmoud Abbas, his “partner,” and he even used the term “West Bank” instead of the biblical name Judea and Samaria.

All of that stirred in Mr. Lieberman the desire to be, as one former associate put it, “the one who made clear that this was unrealistic.”

He actively distanced himself from his government’s policy.

“Being foreign minister didn’t tame him for too long,” a political associate of Mr. Netanyahu’s said of Mr. Lieberman. “He may have made an internal calculation about his future, and he may be angry about being out of the real decision-making process.”

Whatever the reason, Mr. Lieberman’s open pressure on Mr. Netanyahu seems to have had an impact. Mr. Lieberman wants a loyalty oath to be a requirement in Israel because of concerns about Israeli Arabs.

This week, a long-delayed bill requiring non-Jews who immigrate to Israel to declare their loyalty to Israel as a Jewish and democratic state suddenly was given government backing. So was a bill to require a popular referendum before land could be yielded in any peace deal.

And Mr. Netanyahu called from the Parliament podium for the Palestinian leadership to acknowledge Israel as the Jewish nation-state.

Not everyone thinks Mr. Netanyahu’s attention to these issues was the result of pressure from Mr. Lieberman.

Aluf Benn wrote Wednesday in the left-leaning newspaper Haaretz that Mr. Netanyahu favored much of the agenda associated with Mr. Lieberman and two other right-wing ministers.

“The leader of Yisrael Beiteinu has enthusiastically headed the struggle to oppress the Arab community, while breathing down his neck are ministers Eli Yishai and Yaakov Neeman,” he wrote. “But they are only the flag-bearers. Prime Minister Benjamin Netanyahu is hiding behind them. He is the instigator of this policy, although he rarely expresses himself in the same provocative vein.”

Mr. Benn’s thesis, in part, is that Mr. Netanyahu believes that the left can return to power only with support of the 20 percent of the population that is Arab. The more alienated the Arabs feel, the less likely they are to vote, leaving the arena empty for the right and a contest between Mr. Netanyahu and Mr. Lieberman — a contest he feels he can win.