BEIRUT, Aug 28 (Reuters) - Lebanon's opposition leader Michel Aoun, Hizbollah's main Christian ally, urged the cabinet on Monday to resign, citing what he said was its failure to handle the crisis during Israel's war with the guerrilla group.

The retired army general, who in the past had demanded that Hizbollah disarm but later strengthened his ties with the Shi'ite Muslim group, appeared to threaten unrest if the cabinet of Prime Minister Fouad Siniora did not resign peacefully.

"We hope... a very peaceful change takes place, preserving stability in the country. If this change does not happen in such a way, there are other ways to escalate from now on," he told a news conference.

Aoun's remarks came as U.N. Secretary-General Kofi Annan was meeting Siniora, a member of the country's majority anti-Syrian coalition, and his ministers. Annan arrived in Beirut earlier in the day on the start of a regional tour to shore up a truce between Israel and Hizbollah that ended a 34-day war.

Hizbollah's leader Sayyed Hassan Nasrallah called in an interview broadcast on Sunday for a national unity government including Aoun, without demanding more power for Hizbollah, which has two cabinet ministers in the current coalition.

Aoun, who has a major parliamentary bloc but is not part of the cabinet, said there were "big questions about the government's behaviour" during the war, ignited by Hizbollah's July 12 capture of two Israeli soldiers in a cross-border raid.

Siniora's government has condemned the Israeli attacks on Lebanon but said from the outset it did not endorse Hizbollah's operation. Hizbollah has criticised the government for what it described as its slow moves to extend aid and to help in rebuilding the areas destroyed by Israeli attacks. "Once this government is changed, there will be a new government 100,000 times better," said Aoun, who declined to say if his Free Patriotic Trend would take part in the new cabinet.

Aoun, who hopes Hizbollah will back him in Lebanon's 2007 presidential elections, supported the group's resistance against Israeli attacks and agreed with its reservations over the U.N. Security Council resolution that ended the fighting.

He also agreed with its rejection of an Israeli demand that U.N. peacekeepers should deploy along Lebanon's border with Syria to prevent arms shipments from reaching Hizbollah.

"Do they (U.N. troops) want to come to our toilets and monitor what we do there as well?" he said.

The government has said the Lebanese army is capable of controlling the border crossing to prevent arms smuggling.