The official, Deven Sharma, president of Standard Poor’s, added that deficit-reduction plans currently being considered in Congress could be enough to allow the United States to keep its triple-A credit rating.

But Mr. Sharma declined to specify what level of cuts would be needed to maintain the top-level credit rating.

He said news articles last week “misquoted” a July 14 S. P. report as saying that Congress would need to achieve at least $4 trillion in spending cuts over 10 years to maintain the country’s triple-A rating.

A cut of $4 trillion, a number that is cited in the S. P. report and that has been the focus of concern on Wall Street over the last two weeks, was “within the threshold” of what S. P. thinks is necessary, Mr. Sharma said. But he declined to draw a bright line, saying only that “some of the plans” currently being considered on Capitol Hill “could bring the U.S. debt burden and the deficit level in the range of a threshold for a triple-A rating.”

The remarks came at a hearing by the Oversight and Investigations Subcommittee of the House Financial Services Committee. The hearing was scheduled to examine the performance of the major credit ratings agencies since changes in policies affecting the companies were instituted as part of the Dodd-Frank Act.

The credit ratings agencies were sharply criticized after the financial crisis for offering top-level ratings on billions of dollars of mortgage-backed securities that later lost substantial value when the housing market collapsed.

But the hearing quickly turned to the issue of what would happen if the nation were unable to meet its obligations because Congress did not raise the federal debt ceiling.

Pressed by Representative Scott Garrett, a New Jersey Republican, on whether the deficit-reduction plans put forth by the Obama administration or Senate Democrats would be sufficient to maintain the country’s credit rating, both Mr. Sharma and Michael Rowan, global managing director in the commercial group of Moody’s Investors Service, declined to comment.

Banking regulators who testified at the hearing were less hesitant to give their views about how a downgrade of the country’s credit rating would affect the financial markets and banks.

David K. Wilson, senior deputy comptroller and chief national bank examiner in the Office of the Comptroller of the Currency, said that members of Congress were “right to worry” about the possible unknown effects of a downgrade.

At the least, he said, borrowers would have to increase the amount of Treasury securities they offered as margin, or collateral for loans. A downgrade of the country’s credit rating would probably also be followed by lower ratings on state and local government debt, he said.

Any difficulties would be “manageable in the short term” because even a downgrade to AA from the current AAA rating would still mean that Treasuries were “very high-quality securities,” Mr. Wilson said. The long-term effects of a ratings downgrade, he added, were unknown.

Asked by Representative Brad Miller, a Democrat from North Carolina, if he were “right to worry that this could be real bad if our debt were downgraded,” Mr. Wilson replied, “You know, it’s hard to measure, but I think you’re right to worry. I mean, it could happen. It could be a big thing.”

Representatives from the Federal Reserve, the Securities and Exchange Commission and the comptroller’s office all said they believed that the credit rating agencies were doing a better job of accurately assessing risks in their credit ratings now than they were before the financial crisis.

However, Mark E. Van Der Weide, senior associate director in the division of banking supervision and regulation at the Federal Reserve, said “the crucial thing is that no matter how good we think they’re doing, we not over-rely on them — not the government, not the private sector.”

Republican members of the panel also asked Mr. Sharma whether Treasury Department officials had pressured the company not to downgrade the United States credit rating.

In an April 27 letter to the Treasury secretary, Timothy F. Geithner, Representative Randy Neugebauer, a Texas Republican who is chairman of the oversight subcommittee, questioned the appropriateness of the government protesting ratings changes “given its regulatory and oversight role over the agencies.”

In a June 13 response, Mr. Geithner said the department had “entirely appropriate” contacts during the ratings review process with Standard Poor’s, which, he noted, “we do not regulate or oversee.”

Mr. Sharma told the committee that its contacts with Treasury, which included the sharing with the department a draft news release about S. P.’s decision to put the United States’ credit ratings under review for a possible downgrade before the move was announced to the public, were “standard operating process.”

This article has been revised to reflect the following correction:

Correction: July 27, 2011

An earlier version of this article incorrectly said that officials from two credit rating agencies said the United States was unlikely to default.

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