A rift within the ruling Liberal Democratic Party triggered by the revolt of former Secretary General Koichi Kato deepened further on Monday as two party factions backed Kato's rebellion against Prime Minister Yoshiro Mori.

Heavyweights within the party have been trying to quell the turmoil, with LDP President Mori and Secretary General Hiromu Nonaka indicating they are ready to talk with Kato.

Kato intensified his challenge against Mori over the weekend by suggesting he may back a no-confidence motion expected to be filed against Mori's Cabinet by the opposition camp later this month.

On Monday, senior members of two LDP factions, one led by Kato and another by his longtime ally Taku Yamasaki, gathered separately to confirm their unity in supporting Kato.

"I explained the recent development and was very grateful as (my faction members) said they will stay united and support me," Kato told reporters after the gathering in Tokyo. "I will consult my fellow members on whether I should meet with the prime minister."

Acting in concert with Kato's call, the Yamasaki faction announced it would demand the resignation of Mori and support Kato as his successor.

Meanwhile, other LDP leaders agreed to lay siege to the Kato-Yamasaki rebellion while maintaining their business-as-usual manner.

"Despite some problems within our party, (the leaders) agreed that the entire party will put its effort behind this difficulty and get important bills, including the supplementary budget, passed through the Diet," Nonaka said following an LDP executive meeting in the evening.

At a liaison meeting for leaders of the tripartite ruling coalition on Monday afternoon, New Komeito chief Takenori Kanzaki warned LDP officials to clear up the turmoil over Kato's remarks as soon as possible to avoid a disruption in the Diet.

"We (LDP members) will all have to take responsibility if we continue such an internal quarrel. We should do our utmost to avoid any possible confusion," former Prime Minister Ryutaro Hashimoto said in a speech in Tokyo. Hashimoto is chairman of the LDP's largest faction.

In a Sunday interview with NHK TV, Kato hinted he may support the motion the opposition camp has threatened to submit against Mori later this month.

Earlier, Kato indicated he and other members of his faction might abstain from a Diet vote on such a motion.

An abstention by 45 Lower House members belonging to Kato's faction plus the 19 members of Yamasaki's group would still enable the LDP and its coalition partners to vote down the no-confidence motion by a slim margin.

But if all members of the Kato and Yamasaki factions join the 190-member opposition camp in voting for the motion, they would far outnumber the ruling bloc -- the LDP, New Komeito and the New Conservative Party. Yamasaki has indicated he will join hands with Kato.

"There may be no big difference between casting a vote in favor and abstaining," Kato told NHK.

Also in remarks to reporters later in the day, Kato said, "I will not rule out various options in case we come to a deadlock."

If the no-confidence motion clears the Lower House, Mori has to either quit or dissolve the Lower House and call a general election.

Kato, head of the LDP's second-largest faction and long viewed as the most likely successor to Mori, denied speculation that he may bolt from the LDP.

"I will not leave the LDP, though I understand such speculation has emerged." Kato said. "I have been at the core of the LDP for some time."

But top LDP leaders who have confirmed their support for Mori against the challenge from Kato say party members who support the no-confidence motion against Mori could be expelled from the party.

On Sunday afternoon, Kato visited the Tokyo home of Finance Minister Kiichi Miyazawa, who formerly headed Kato's faction, to brief the minister on his demands for Mori to step down.

Miyazawa told reporters after the meeting that he had told Kato, "In my capacity (as a Cabinet minister under Mori), I hope you have enough self-restraint not to do such a thing."

The finance minister also asked Kato to discuss the matter with other party members and to hold talks with Mori.

Kato told reporters he had agreed to try to meet the prime minister at an appropriate time.

Mori meanwhile met his aides, including Fukuda and Deputy Chief Cabinet Secretary Shinzo Abe, at his Tokyo residence Sunday to discuss the situation.

In Kyoto, Nonaka said he doubts Kato has made a final decision on whether to support the planned no-confidence motion.

"Apparently, he has not made up his mind. He must be thinking his comments have been exaggerated by the media, causing bigger ripples than he expected," Nonaka told reporters in his hometown after the NHK program was aired.

The secretary general also called on Kato to be prudent, saying members of his faction, including Miyazawa and Makoto Koga, chairman of the LDP's Diet Affairs Committee, have been working hard to pass important bills through the Diet.