UNITED NATIONS, Nov 15 (Reuters) - U.N. Secretary-General Kofi Annan plans to send to the Security Council within 24 hours his plan for a special court to try suspects in the murder of former Lebanese Prime Minister Rafik al-Hariri, the United Nations said on Wednesday.

The statement by U.N. chief spokesman Stephane Dujarric came a day after Lebanon's pro-Syrian president, Emile Lahoud, wrote Annan that the Lebanese government's approval of the plan had been illegitimate because he had not himself approved it.

Lahoud also said the Cabinet session that approved the draft was illegitimate. Six pro-Syrian opposition ministers, including all of the Shi'ite Muslims in government, did not attend the session.

But Dujarric told reporters, "We are moving on with the process and the secretary-general intends to submit his report to the Security Council within 24 hours."

The United States has called for quick Security Council action to approve the plan so the court can be set up quickly and be ready to start work once a U.N. inquiry identifies suspects in the case.

Five ministers from Shi'ite groups Hezbollah and Amal quit the Cabinet on Saturday when talks over giving the opposition a greater say in government collapsed.

A sixth minister, loyal to Lahoud, resigned on Monday before the Cabinet session.

Lahoud said the Monday Cabinet decision did not bind the Lebanese state, although he added he supported the idea of the tribunal, "but with regulations."

The U.N. commission investigating Hariri's assassination has implicated senior Lebanese and Syrian security officials in the killing, although Damascus denies involvement.

Hariri was killed in a Feb. 14, 2005, truck bombing shortly after speaking out against Syria's decades-long domination of Lebanon, and his murder was followed by 14 other attacks that killed or wounded anti-Syrian politicians and journalists.

Work on the tribunal began after anti-Syrian Prime Minister Fouad Siniora asked Annan last December for help in bringing the killers to justice once they were identified.