The Bush administration says it intends to remain engaged in efforts to achieve Middle East peace despite mounting evidence that Yasser Arafat's Palestinian Authority was behind an effort foiled by Israel last week to smuggle in tons of Iranian weapons. U.S. officials are also implicating the Lebanese guerrilla group Hezbollah in the operation.

Officials here say there is convincing evidence that senior figures in the Palestinian Authority, if not Mr. Arafat himself, were involved in the arms smuggling scheme, along with Iran and the Lebanese guerrilla group Hezbollah.

Israeli forces last week seized a ship in the Red Sea that was manned by Palestinians and loaded with some 50 tons of Iranian weapons including "Katyusha" rockets, anti-tank missiles and advanced plastic explosives.

Both Israeli and U.S. analysts say delivery of the weapons could have lead to a dramatic escalation of the Israel-Palestinian conflict that has been underway for more than 15 months.

However, in a talk with reporters at the White House, President Bush said the smuggling affair will not mean an end to U.S. efforts to broker an Israeli-Palestinian cease-fire and renewed peace talks.

"You asked a question: should we basically disengage? And the answer is no, we won't disengage from the Middle East. We will stay involved in the Middle East peace process, or trying to get to the peace process. And it starts with making the region more secure," he said. "Mr. Arafat must renounce terror and must reject those in the region that would disrupt the peace process by use of terrorist means."

Mr. Bush said U.S. envoy Anthony Zinni, who returned from his second mission in the region last week, would be sent back "at the appropriate time" to continue his effort to get the parties to implement a permanent cease-fire.

The smuggling episode has cast a pall over Bush administration peace efforts launched by Secretary of State Colin Powell with a policy speech nearly two months ago.

At a joint appearance here with Mexican Foreign Secretary Jorge Castaneda, Mr. Powell said the United States was pressing Mr. Arafat and his colleagues to account for the incident.

"This is a very serious matter. They have to give it their immediate attention. They have to conduct whatever inquiries or investigations are necessary to get to the bottom of this matter," he said. "We are deeply disturbed by the arrival of this ship in the region and the fact that could have completed its mission and off-loaded weapons that would have been put to the worst kind of use against Israel and others in the region. Glad the Israelis intercepted it, and now we have to find all those responsible and accountable for this incident."

Mr. Powell said he had not seen information directly linking Mr. Arafat with the smuggling case but other U.S. officials say they strongly suspect that he knew about the operation despite his denials.

State Department spokesman Richard Boucher said the weight of the evidence is "compelling" about Iranian and Hezbollah involvement as well.

Israeli intelligence officials who briefed U.S. authorities on the incident Wednesday said Hezbollah personnel loaded the ship on an Iranian island a month ago, and coached the Palestinian crewmen on how to get the weapons past Israeli patrols along the Gaza coast.