JERUSALEM — Avigdor Lieberman, Israel’s blunt-talking and polarizing foreign minister, will be charged with breach of trust but not with fraud and money laundering, prosecutors announced Thursday, ending an investigation lasting years and throwing a curve into Israel’s coming elections.

Mr. Lieberman, 54, and his lawyer both said Thursday that they saw no immediate reason for him to resign, though his political opponents and some news media figures called on him to do so, citing a Supreme Court ruling that forced other ministers to quit when criminally charged. He leads the secular, ultranationalist Yisrael Beiteinu faction, which has joined forces with Prime Minister Benjamin Netanyahu’s Likud Party for the Jan. 22 elections, and he is widely considered one of Israel’s most powerful and popular politicians.

“We are 40 days away from elections, and we must win these elections with a much more convincing victory, so ultimately the decision will be made together with legal opinions and after considering the well-being of the voters,” Mr. Lieberman said at a party gathering in Tel Aviv on Thursday night.

More cheerful than defiant, he said he had been hounded by corruption accusations since July 1996, when he served as a top aide to Mr. Netanyahu during his first term as prime minister. “Since then till today, not a day has passed without me being referred to as ‘a suspect,’ ‘being under investigation,’ ‘being an intelligence target,’ ” Mr. Lieberman said. “This has been one long and rolling case, receiving a different title every now and then.”

The conduct for which Mr. Lieberman will face indictment stems from an investigation into other allegations. He is accused of promoting Israel’s former ambassador to Belarus for another post after the ambassador gave him confidential information regarding an Israeli police investigation into Mr. Lieberman’s activities.

But Mr. Lieberman will not face charges on the underlying, more serious case, in which he was suspected of receiving millions of dollars from international tycoons with business interests in Israel through companies formally led by family members or associates.

Israel’s attorney general, Yehuda Weinstein, said Thursday in a report announcing his decision that he could not adequately prove a link between Mr. Lieberman and the money, though he said, “The suspicions against Lieberman’s series of intricate and intertwined, underhanded actions cannot be ruled out.”

“In a case of this nature, the expected fear arises: that a wrong message might be sent to the public by such a decision, as if the prosecution is not armed with enough ‘spirit of battle’ in its war on corruption,” Mr. Weinstein wrote in the report. “It must be reiterated that closing a criminal case due to insufficient evidence does not constitute a certificate of kashrut,” or kosher certification.

Amir Oren, a columnist for the left-leaning Haaretz newspaper, wrote: “Lieberman has won. Justice has lost.”

Born in Moldova, Mr. Lieberman is a populist with wide support among Israel’s one million immigrants from the former Soviet Union. He lives in a West Bank settlement considered illegal under international law, and he is perhaps the government’s harshest critic of President Mahmoud Abbas of the Palestinian Authority, having called for his ouster and denounced as “diplomatic terrorism” his recent bid for upgraded Palestinian status at the United Nations.

Polls have consistently shown that Mr. Lieberman’s joint ticket with Mr. Netanyahu, known here as Likud Beiteinu, is expected to receive 39 to 40 of the 120 seats in Israel’s next Parliament, by far the largest bloc. The merger was seen as crowning him Mr. Netanyahu’s successor as leader of Israel’s right flank, and a top contender to eventually follow him as prime minister.

Mr. Netanyahu on Thursday gave no hint of suggesting that his sidekick step down. “I believe in Israel’s legal system and respect it,” the prime minister said in a statement. “The right that it grants any Israeli citizen to defend himself also extends to Minister Lieberman, and I hope for him that he’ll be able to prove that he’s also innocent regarding the only case that remains.”

But opposition leaders said that if Mr. Lieberman did not resign voluntarily, they would seek his ouster in court.

The Labor Party issued a statement saying that his conduct “endangered and still endangers Israeli democracy and the rule of law.”

Yair Lapid, head of the centrist Yesh Atid party, said it was “unthinkable” that Mr. Lieberman would “keep his government post and keep representing Israel around the world.”

On Thursday, Moshe Negbi, a legal commentator on Israel Radio, said, “There is no question that Avigdor Lieberman will have to say goodbye to his seat.”

But Aviad Hacohen, a law professor at Bar Ilan University, said he “would not eulogize Lieberman too quickly,” arguing that the case against him is less serious than those that cost other ministers their seats.