Lebanon's prime minister has threatened to step down if the country's Cabinet refuses to fund a U.N.-backed tribunal investigating the 2005 assassination of a Lebanese statesman. The move would almost certainly plunge the deeply divided country into a political crisis.

In a televised interview broadcast late Thursday, Najib Mikati said he refused to head a government that did not honour Lebanon's obligation to support the Netherlands-based court investigating the death of former prime minister Rafik Hariri.

"I refuse to be in a post in which Lebanon fails to commit to its international obligations," Mikati said in the interview with the local LBC TV station. "By resigning, I would be protecting Lebanon."

The investigation, and the degree to which the Lebanese authorities should co-operate with it, has become one of the most controversial issues in Lebanese politics in recent years.

Mikati's stance in favour of co-operation is in stark contrast with some of his allies, including the Shiite Muslim Hezbollah group, which strongly backed him as prime minister five months ago.

Hariri was killed by a suicide truck bomb on Feb. 14, 2005, in one of the most dramatic political assassinations in the Middle East. A billionaire businessman, he was at the time Lebanon's most prominent politician.

The U.N. and the Lebanese government subsequently instituted a Special Tribunal for Lebanon to investigate the case. It has since indicted four members of the Iranian-backed Hezbollah in the slaying.

The group denies any role in the assassination. The group's leader has denounced the tribunal as a foreign conspiracy and has vowed that he will not to allow a Hezbollah member be arrested for the killings.

The Hezbollah-backed government of Mikati now faces a deadline for agreeing to pay Lebanon's 49 per cent share in the tribunal for this year. Hezbollah and its allies, who hold the majority of seats in Mikati's government, have rejected its funding by the Lebanese government. They consider the court to be illegitimate.

The issue is to be discussed at a crucial Cabinet session next week.

Mikati was Hezbollah's pick for prime minister five months ago when he replaced Saad Hariri, the slain prime minister's son. Hariri was ousted from his post by Hezbollah and its allies for his refusal to end Lebanon's co-operation with the tribunal.

Western countries have hinted at possible sanctions if Lebanon fails to co-operate.

US Ambassador to Lebanon Maura Connelly warned this month that a failure by the Lebanese government to meets its obligation to the tribunal could lead to "serious consequences."

Mikati, in the interview, said he wanted to spare Lebanon the consequences.

He urged politicians in Lebanon to do the right thing and to think of the funding issue as "an insurance police" for Lebanon.

"As a prime minister, I need to preserve Lebanon," he said.