BAGHDAD - Despite a more pessimistic outlook voiced in Washington, a top American official expressed confidence yesterday that the United States and Iraq will complete a long-term security pact on time next month.

David Satterfield, the State Department's top adviser on Iraq, said both sides were committed to reaching an agreement, which would also provide a legal basis for keeping U.S. troops here after the U.N. mandate expires at the end of the year.

"We're confident it can be achieved, and by the end-of-July deadline," Satterfield said of the agreement, which has generated a storm of criticism from Iraqi lawmakers who must ratify the deal.

Satterfield bristled at suggestions by a senior Bush administration official close to the talks, who told the Associated Press on Monday that it was "very possible" the United States might have to extend the existing U.N. mandate.

"It's doable, that's where our focus is, not on alternatives," Satterfield told reporters. "We're focused on Plan A because we believe Plan A can succeed. . . . We think it's an achievable goal."

Stakes for both sides are high. An agreement would ensure long-term U.S. political and military support for Iraq and could help ease Arab concerns that the country would fall under Iranian domination if U.S. troops leave.

The agreement, which has sparked strong opposition from Iran, also could serve to counter the spread of Iranian influence both in Iraq and the wider Middle East.

However, the deal is politically explosive in a country where many people are weary of the American military presence, considered an affront to Iraqi national pride.

Iran fears that if long-term U.S. military bases are established on Iraqi soil, Iraq could be used as a launching pad for attacks on the neighboring country.

Satterfield disputed that yesterday, saying Washington "does not think Iraq should be an arena, a platform for attacks on other states."

"We want to see Iraqi sovereignty strengthened, not weakened," Satterfield said.

He added that "parties outside Iraq" who demand respect for Iraqi sovereignty "should be sure they're respecting Iraq's sovereignty" - a clear reference to U.S. allegations that Iran arms and trains Shiite militants here.

Deputy Prime Minister Bahram Saleh told reporters yesterday that Iraq wanted to deepen its relationship with the United States "to serve our country, to preserve our independence and sovereignty from internal and external security challenges."

Without mentioning Iran, he said the agreement would not be "in any form a threat to others."

"Iraq also needs assurances from the neighboring countries to protect its sovereignty and stop any interference in its internal affairs," he added.

Also yesterday, the chief of Saddam Hussein's tribal clan was killed by a bomb glued to the undercarriage of his car in Tikrit, a mostly Sunni Arab city about 80 miles north of Baghdad, Iraqi police said. Sheikh Ali al-Nida, 65, was the leader of the al-Bu Nasir tribe, a large Sunni Arab clan of about 20,000 members, including Hussein's family.

Nida received Hussein's body after his 2006 execution and arranged the former dictator's funeral. In 2007, he founded a so-called Awakening Council in Hussein's home village of Ouja, partnering with U.S. forces to fight Sunni militants in the area.