Updated

Former Foreign Minister Avigdor Lieberman went on trial Sunday on fraud and breach of trust charges, pleading innocent in a case that could have deep implications for the makeup of Israel's next government.

Lieberman, the leader of the ultranationalist Yisrael Beitenu Party and a key ally of Prime Minister Benjamin Netanyahu, is accused of trying to advance the career of a former diplomat who relayed information to him about a separate criminal investigation into Lieberman's business dealings.

The outcome of the trial will determine whether the hardline Lieberman will be able to return to the Israeli Cabinet or whether his fast-rising political career will come to a premature end.

Lieberman's Yisrael Beitenu ran on a joint list with Netanyahu's Likud Party in a parliamentary election last month. Their combined bloc emerged as the largest faction in the legislature and is expected to be the dominant member of the next ruling coalition. Netanyahu is still negotiating with potential coalition partners.

Lieberman has made clear that he wants to return to the Foreign Ministry, but he is barred from serving in the Cabinet while he is on trial. He has said that if he's convicted, he will resign from parliament. Depending on the severity of the conviction, Lieberman could be barred from seeking office again for years to come. In the meantime, he is allowed to serve in parliament.

The situation has put Netanyahu in a delicate position. With the trial expected to last well into the spring, it is not clear whether Netanyahu is willing or able to hold open the important foreign minister's job for his political ally. If he offers the post to another party, however, his alliance with Lieberman could become strained.

Lieberman and his Yisrael Beitenu faction have accumulated tremendous political power, and he is a key player in the governing coalition Netanyahu is now trying to form. Many speculate he is preparing for a run as prime minister in future elections.

Netanyahu has been serving as acting foreign minister while he puts together a new coalition. He has until mid-March to form the government.

Lieberman showed little emotion as he arrived at the Jerusalem courthouse on Sunday. His lawyers said they would seek a quick resolution to the case. The trial is scheduled to last until May at the least.

The Soviet-born Lieberman is one of the most contentious and polarizing figures in Israeli politics. Yisrael Beitenu is especially popular among immigrants from the former Soviet Union. With a tough-talking message that has questioned the loyalty of Israel's Arab minority, criticized the Palestinians and confronted Israel's foreign critics, he has at times alienated Israel's allies while becoming an influential voice in Israeli politics.

Lieberman pushed a series of legislative proposals that critics said were anti-Arab, including a failed attempt to require Israelis to sign a loyalty oath or have their citizenship revoked. He also embarrassed Netanyahu in the past by expressing contrasting views to that of the government, including skepticism over the chances of reaching peace with the Palestinians.

Lieberman was largely sidelined in Israel's dealings with the United States. Netanyahu himself or the outgoing defense minister, Ehud Barak, usually handled ties with Washington instead.

Former Deputy Foreign Minister Danny Ayalon, who was unceremoniously dropped from Lieberman's faction list just weeks before elections and who will likely testify against Lieberman in his trial, was quoted by the Maariv daily as saying that Lieberman is unsuited to serve as the nation's top diplomat because he did not win the international community's trust.

"If after four years of service this is the result, he should go for the Finance Ministry post," Ayalon was quoted as saying.