Palestinian leader Yasser Arafat has sent Secretary of State Colin Powell a letter that U.S. officials say pledges an end to arms smuggling attempts by his Palestinian Authority. It also promises a halt to Palestinian military cooperation with Iran.

The Bush administration had maintained that despite Mr. Arafat's denials, Palestinian Authority figures were involved in the effort -- foiled by Israel last month -- to smuggle in a boatload of Iranian arms.

And officials here are welcoming his letter as a positive development -- though State Department spokesman Richard Boucher says it remains to be seen if he will follow up his promises with action. "We see it as a positive letter. We're currently studying it. I would none-the-less point out that as we've said many times, action must follow words," he says. "And we hope not to see strong resolute and irreversible action by Chairman Arafat and the Palestinian Authority along the lines that he indicated in the letter."

A senior U.S. official who spoke to reporters here said that in the letter -- delivered to the U-S consulate in Jerusalem and passed on to Washington - the Palestinian leader made no attempt to deny a Palestinian role in the smuggling affair and promised there would be no recurrence of such activity.

Mr. Arafat was also said to have pledged an end to "any form" of military or arms cooperation between the Palestinian Authority and Iran.

The development in the smuggling affair came as U.S. officials were expressing deepening concern about escalating Israeli-Palestinian violence, including an unprecedented gun attack outside an Israeli army base in the southern town of Beersheva Sunday and retaliatory Israeli air strikes in Gaza.

Mr. Boucher, in particular, said the use by Palestinian militants of long-range "Qassam-Two" artillery rockets in clashes with Israel for the first time was a "dangerous and provocative escalation," but he also criticized Israeli air operations as "counter-productive" to efforts to reduce violence and restore calm. "Though we understand the need for Israel to take steps to insure its self-defense, we're seriously concerned about Israeli attacks over the past several days on Palestinian Authority facilities, particularly in areas that are heavily populated by civilians," says Mr. Boucher. "We're especially concerned by attacks on or near Palestinian prison facilities, reported releases of prisoners detained in those areas, and reports a United Nations facility was struck, with possibly a U.N. official wounded."

The State Department gave no indication of an early resumption of the suspended Middle East cease-fire mission of U.S. envoy Anthony Zinni.

But Mr. Boucher said Secretary Powell had spoken by telephone with British Foreign Secretary Jack Straw and German Foreign Minister Joschka Fischer --both of whom are preparing to go to the region this week - in order to coordinate U.S. and European efforts.