Undersecretary of State Michael H. Armacost said yesterday that Iraq's resumption of attacks on Iranian ships in the Persian Gulf was "very regrettable, extremely unfortunate" and said the action will increase the risk that Iran will retaliate against U.S.-protected Kuwaiti oil tankers.

Armacost added that the timing of the Iraqi attacks was particularly "deplorable" since they came at a time when Iran was under considerable international pressure to accept a mid-July U.N. Security Council resolution demanding a cease-fire in the seven-year-old war.

Armacost nonetheless noted that given Iran's refusal to accept the U.N. cease-fire resolution, the Iraqi decision was "not entirely unexpected" and "understandable," effectively sending a mixed administration signal on Iraq's sudden resumption of the "tanker war." He was interviewed on NBC News' "Meet the Press."

The renewed Iraqi attacks and Iran's threat to retaliate have placed the United States in a delicate military and diplomatic position in the gulf. They have increased the possibility of a direct clash between U.S. and Iranian forces and could undermine the administration's diplomatic drive at the United Nations to obtain a cease-fire.

Some U.S. analysts said it is particularly ironic that Iraq, which the administration has been trying to help with its new activist gulf policy, had caused the new complications for the United States with its renewed attacks.

An earlier Iraqi action -- the May 17 attack on the USS Stark, which killed 37 American sailors -- sparked hot debate in Congress over the wisdom of the administration's decision to become so deeply involved in the gulf by providing military protection for 11 Kuwaiti oil and gas carriers.

Despite Armacost's measured public response, several administration officials privately expressed irritation at the Iraqi decision to break the 45-day lull in the war.

In the past week, both Iraq's ambassador here, Nizar Hamdoon, and its chief delegate to the United Nations, Ismat Kittani, warned that a renewal of Iraqi attacks on Iranian oil facilities in the gulf was imminent.

State Department spokesmen here and diplomatic sources in the gulf said that the United States and Britain had been pressing Iraq not to resume the war, particularly with pressure building on Iran to accept the U.N. resolution.

In London, the British foreign secretary, Sir Geoffrey Howe, said he was "dismayed" by the Iraqi action and called it "a dangerous escalation" in the war.

Senior administration officials indicated as late as Friday that they thought the Iraqi threats to resume attacks in the gulf were probably just part of Iraq's diplomatic maneuvering to increase the pressure on Iran.

Senate Minority Leader Robert J. Dole (R-Kan.) said on CBS News' "Face the Nation" that he understood the administration was talking to the Iraqis in an attempt "to get them to back off."

Armacost said "undoubtedly the risks are increased" for the U.S.-escorted Kuwaiti tankers as a result of the Iraqi attacks, "at least to take their {the Iranians'} statements at face value."

"We have a larger array of ships ourselves in the gulf. In one sense that exposes us somewhat more," Aramcost said, referring to the more than 30 U.S. warships now assembled in the gulf or the nearby northern Arabian Sea.

But Armacost defended the big U.S. military buildup there, saying that "by accumulating great power we also have a greater capacity to defend ourselves and to deter any provocation directed against us or those ships we're protecting."

Armacost's reaction to the resumed Iraqi attacks appeared deliberately ambiguous.

"I'm saying Iraq had been warning that a failure by Iran to comply {with the U.N. resolution} would leave them in a position where they couldn't allow the ground war to continue and escalate despite the Security Council resolution without some response in the gulf," he said.

"So I find it {the timing} deplorable but I also say in terms of their interests it's understandable," he added.

He said the United States shared Iraq's demand for a comprehensive cease-fire on land, sea and air. "It's up to Iran to declare itself firmly in support of and in compliance with the Security Council {cease-fire} resolution," he added.

Armacost said he hoped the resumption of Iraqi attacks would provide incentive for the U.N. Security Council to consider a second resolution imposing an arms embargo, or other sanctions, on Iran in a bid to force its compliance with the cease-fire resolution.

"The resumption of attacks lends greater urgency to moving beyond the . . . {U.N. cease-fire} resolution passed on July 20 and put some teeth into the second resolution." he said.

The administration has already begun pushing for consideration of this resolution, but the Soviet Union has indicated it believes it is "premature" because Iran still has not formally rejected the U.N. cease-fire demand.

China, another of the five permanent U.N. Security Council members, is now the main provider of weapons to Iran, according to U.S. estimates, and also is unlikely to be enthusiastic about an arms embargo.

Foreign correspondent Richard Weintraub contributed to this report.