BAGHDAD, Iraq – Iraq’s interim prime minister yesterday warned that efforts to resolve the standoff in Fallujah peacefully have entered their “final phase” and said he will not hesitate to launch “a military solution” to end Sunni terrorists’ hold over the city.

In another city of Iraq’s stormy Sunni Triangle, a rocket slammed into the Sunubar Hotel in Tikrit late yesterday, killing 15 Iraqis and wounding eight others, hospital officials said. Terrorists may have been aiming at an American position, which was targeted by a second rocket. American officials said no American casualties were reported.

Prime Minister Allawi’s warning, delivered in a nationally televised news conference, occurred as American forces prepare for a showdown with thousands of terrorists holed up in Fallujah – the city that has become the focal point of armed resistance to the Americans and their Iraqi allies.

Mr. Allawi appeared to be aiming to prepare the Iraqi public for an onslaught likely to unleash strong passions, especially among the country’s Sunni Muslim minority. He warned of civilian casualties, saying that if he orders an assault it would be with a “heavy heart,” because “there will be some loss of innocent lives.”

“But I owe, owe it to the Iraqi people to defend them from the violence and the terrorists and insurgents,” he said.

American and Iraqi commanders want to put down guerrillas before vital elections due to be held by January 31, which Mr. Allawi insisted will take place as scheduled. Yesterday, insurgents in Fallujah fired mortar rounds and rockets at American Marines, who responded with artillery.

American aircraft also struck suspected rebel positions, Marine officials said. Clashes were also reported between American forces and insurgents in Ramadi, west of Fallujah, killing seven Iraqis and injuring 11, hospital officials said.

As night fell in the Iraqi capital, the rumble of powerful explosions could be heard coming from the western edge of the city but the cause of the blasts could not be determined.

The blast in Tikrit, 80 miles north of Baghdad, sent frightened guests of the three-story hotel running into the street, some barefoot, others with bloodstains on their clothes.

American military officials blamed the attack on “anti-Iraqi forces,” the term they use for insurgents. They said two rockets were fired, one of which exploded near an American military position but caused no damage or casualties.

American officials say Mr. Allawi will personally issue the final order to launch any all-out assault on Fallujah and other Sunni insurgent strongholds north and west of the capital.

Mr. Allawi gave no deadline for talks with Fallujah city leaders to bear fruit, but he insisted they must hand over foreign fighters and allow Iraqi security forces to take control of the city.

“We have now entered the final phase of attempts to solve Fallujah without a major military confrontation. I hope we can achieve this, but if we cannot, I have no choice but to secure a military solution,” he added.

Mr. Allawi also said authorities have arrested 167 Arab foreign fighters, who are in Iraq’s custody. He said the government had identified financiers abroad and would ask other Arab governments to send them back for prosecution.

Sunni clerics have threatened to call for a nationwide civil disobedience campaign and to boycott national elections in January if the Americans attack Fallujah.

Fallujah has become the nexus of an insurgent network that has carried out numerous car-bombings and beheadings of foreign hostages since the Bush administration ordered Marines to halt an offensive against the city in April.