WASHINGTON— A top executive of Halliburton Company told lawmakers here yesterday that the corporation does not intend to resume business in Iran now that it has completed its current contracts.

Testifying before a Senate subcommittee investigating American business ties to Iran, a Halliburton vice president and corporate secretary, Sherry Williams, said that when company officials decided to leave Iran in 2005, “We recognized that we would not be able to go back in” under federal law.

The statement came as welcome news to lawmakers, who raised concerns over a recent comment by the company’s chief executive, David Lesar, who said the company could return to Iran if conditions changed. Along with other American corporations, Halliburton had come under fire for operating a foreign subsidiary, Halliburton Products and Services Limited, in Iran. Critics said the company was undermining America’s national security interests by exploiting a loophole in federal economic sanctions against Iran as a state sponsor of terrorism.

Ms. Williams also confirmed a company announcement last month that Halliburton had completed its contracts in Iran and was no longer operating in the country.

The New York City comptroller, William Thompson Jr., testified before the Senate panel yesterday to urge Congress to pass a bill that would close the loophole and bar American companies from using foreign subsidiaries that do business in rogue nations.

“Only the passage of tough legislation can ensure that no new firms will take such measures,” Mr. Thompson said.

As comptroller, Mr. Thompson manages more than $100 billion in public pension funds for the city. The city has about $30 million invested in Halliburton, including $10 million, or 400,000 shares, in stock owned by the police and fire department pensions, he said. Since taking office in 2002, the comptroller has sought to use the city’s sizable stake to pressure companies to cease operations in Iran. In addition to Halliburton, those corporations in include General Electric, ConocoPhillips, and Aon.

Some officials have called for major institutional investors to divest holdings in companies linked to Iran. In February, a Republican presidential candidate, Mitt Romney, sent a letter to Governor Spitzer and the new comptroller of New York State, Thomas DiNapoli, urging just that.

In an interview after the hearing, Mr. Thompson resisted that approach, saying he would have more leverage with companies like Halliburton by retaining the city’s investment.

He also said his office would soon begin looking at ways to influence international firms not beholden to American law.

Mr. Thompson, a likely mayoral candidate in 2009, drew praise from the lawmakers. The Democratic chairman of the Subcommittee on Interstate Commerce, Trade, and Tourism, Senator Dorgan of North Dakota, referred to Mr. Thompson as an “activist” on the issue and said he had started a national discussion as far back as 2004.

The senators reserved their criticism for Halliburton and other companies taking advantage of the loophole. “Left to their own devices, companies like Halliburton will follow the money, not the morality,” Senator Lautenberg said. The Democrat of New Jersey has introduced a measure that would close the loophole; Senator Clinton is co-sponsoring the bill.

“We have followed U.S. law, and we will continue to follow U.S. law,” Ms. Williams said. The panel did not dispute that claim, but the senators pressed her to explain whether ethical considerations played into Halliburton’s decision to stop its operation in Iran. She declined to answer, saying only that “a number of factors” led to the decision.

The company is under investigation by the Justice Department for its business dealings. Ms. Williams said it was cooperating with the inquiry.