WASHINGTON — A constitutional amendment to outlaw physical desecration of the American flag cleared the House yesterday but faced an uphill battle in the Senate, where an informal survey suggested it is one vote short of passage.

The 286-130 outcome was never in doubt in the House, which had passed the measure or one like it five times in recent years. The amendment's supporters expressed optimism that a Republican gain of four seats in November's election could produce the two-thirds approval needed in the Senate after four failed attempts since 1989.

But an informal Associated Press survey yesterday found 35 senators on record as opposing the amendment, one more than the number needed to defeat it if all 100 senators vote, barring a change in position.

The proposed one-line amendment to the Constitution reads, "The Congress shall have power to prohibit the physical desecration of the flag of the United States."

For the language to be added to the Constitution, it must be approved by two-thirds of those present in each chamber, then ratified within seven years by at least 38 state legislatures.

Last night, Sen. Hillary Rodham Clinton, D-N.Y., said she would vote against the measure. "I don't believe a constitutional amendment is the answer," Clinton, considered by many a possible presidential candidate in 2008, said in a statement.

Sen. Ken Salazar, D-Colo., remained undecided, a spokesman said.

The House debate fell along familiar lines over whether the amendment strengthened the Constitution or ran afoul of its free-speech protections.

Supporters said there was more public support than ever because of emotions after the 2001 terrorist attacks in New York and on the Pentagon. They said detractors are out of touch with public sentiment.

"Ask the men and women who stood on top of the Trade Center," said Rep. Randy "Duke" Cunningham, R-Calif. "Ask them and they will tell you: Pass this amendment."

Critics accused the amendment's supporters of exploiting the attacks to trample the right to free speech.

"If the flag needs protection at all, it needs protection from members of Congress who value the symbol more than the freedoms that the flag represents," said Rep. Jerrold Nadler, D-N.Y., whose district includes the site of the former World Trade Center.

In the Washington state delegation, Democrats Brian Baird and Adam Smith joined Republicans Doc Hastings, Cathy McMorris and Dave Reichert in voting for the amendment. Democrats Norm Dicks, Jay Inslee, Jim McDermott and Rick Larsen voted against the ban.

Since 1789, there have been more than 11,000 attempts in Congress to amend the Constitution; 27 amendments have won ratification. The last, in 1992, prevents Congress from passing a law giving itself a pay raise before the next election. The 26th Amendment, in 1971, lowered the voting age to 18.

One of the most-recent amendments that received congressional approval but failed to gain ratification by states was the Equal Rights Amendment. It would have set into law equality between men and women. The period for states to ratify it expired in 1982.

The last time the Senate voted on the flag-burning amendment, the tally was 63 in favor and 37 against, four votes short of the two-thirds majority needed.

Now, with more than 24 new members, a four-seat Republican gain in the last election and a public still stung by the terrorist attacks in 2001, activists on both sides said the Senate could be within a vote or two of passage.

But the amendment's prospects faded last night, when Democratic Sens. Maria Cantwell of Washington and Mark Pryor of Arkansas said they would oppose it.

Possible presidential contenders who have supported the amendment in the past include Evan Bayh, D-Ind.; Majority Leader Bill Frist, R-Tenn.; Chuck Hagel, R-Neb.; and John McCain, R-Ariz.

Sen. Joseph Biden, D-Del., a likely presidential candidate, has said he would oppose the amendment.

The amendment is designed to overturn a 5-4 Supreme Court ruling in 1989 that flag burning is a protected free-speech right. That ruling threw out a 1968 federal statute and flag-protection laws in 48 states. The law was a response to anti-Vietnam War protesters setting fire to U.S. flags at demonstrations.

The Senate could consider the measure as soon as next month.

Associated Press writer Jim Abrams contributed to this report. Material from the Los Angeles Times is included in this report.