Updated

Foreign Minister Tzipi Livni said Sunday that if she doesn't become Israel's next prime minister, she will lead her governing Kadima Party into the opposition — a move that could indefinitely stall Mideast peacemaking.

It wasn't clear whether Livni, Israel's chief negotiator with the Palestinians, was ruling out a coalition headed by Benjamin Netanyahu's hawkish Likud Party — or angling for better terms for her centrist party should it choose to enter such a coalition.

Kadima captured 28 of parliament's 120 seats in Israeli elections last week, barely edging out Likud, which won 27. But parties that take a hard line on concessions toward the Palestinians won a total of 65 seats, versus 55 for the more moderate camp, meaning it would be easier for Netanyahu to put together a coalition government.

President Shimon Peres is allowed to assign the task to whatever member of parliament he thinks is best able to form a government, and is expected to announce his decision late this week. Both Livni and Netanyahu have called on each other to join a broad-based government, but neither has indicated readiness to serve together.

Livni said Kadima's edge gives it the right to lead the government. "If not, we will continue to fight for what is right from the opposition," she told Kadima lawmakers on Sunday.

Livni's Kadima is in danger of breaking apart, however, if it is relegated to the opposition. The party is an amalgam of hawks and centrists drawn largely from the Likud, and lawmakers might break away and rejoin Likud.

Earlier Sunday, Kadima Cabinet Minister Avi Dichter said Kadima would agree to a power-sharing arrangement in which Livni and Netanyahu would take turns being premier. Israel had such an arrangement in the 1980s, but unlike the present situation, parliament's moderate and hawkish blocs were evenly divided then.

As Israel's chief peace negotiator over the past year, Livni agreed to discuss with the Palestinians all the major issues dividing the two sides — final borders of the Jewish and Palestinian states, the fate of disputed Jerusalem and a resolution of Palestinian refugees' claims.

Netanyahu says the discussion is pointless because the Palestinians aren't ready to govern themselves. He wants to focus on improving the Palestinian economy, on the ground that prosperity would make them more open to peacemaking at an unspecified time in the future.

If Likud and Kadima don't join forces in the next government, the kingmaker would be the ultranationalist Avigdor Lieberman, who wants to redraw Israel's borders to place heavy concentrations of Israeli Arabs under Palestinian jurisdiction. He believes Arabs who remain should be forced to sign a loyalty oath to the Jewish state or lose their citizenship. Lieberman's Yisrael Beitenu is the country's third-largest party, with 15 seats in parliament.

A new government dependent on Lieberman's backing could cripple efforts to negotiate an accord with the Palestinians. That could put the new government into conflict with the U.S., where President Barack Obama has pledged to put Mideast peacemaking high on his agenda.