WASHINGTON — Senate Majority Leader Bill Frist is vowing to pass a constitutional amendment to ban flag-burning — a move that might score points with Southern Republicans who gathered in Tennessee this weekend but is certain to put him at odds with his deputy in the Senate.

Frist sent a release to reporters and an e-mail to supporters last week touting his plans to bring the constitutional amendment to the floor in June.

The measure has been narrowly defeated in the Senate in the past. In his e-mail to supporters of his political action committee, Frist said he would do everything in his power to see that the measure passes this time.

"I believe we have a moral obligation to rise as a body and declare that it is wrong to burn the flag of the United States of America," Frist wrote.

Political analyst Norm Ornstein called that a clear effort to appeal to conservative voters, some of whom were in Memphis attending the Southern Republican Leadership Conference.

"It strikes an emotional chord," said Ornstein, an analyst with the conservative-leaning American Enterprise Institute, a Washington-based think tank.

Frist, who is considering a 2008 presidential run, spoke at the conference on March 11.

A Frist spokesman said the Tennessee Republican previewed the flag issue now because he recently promised during a meeting with veterans to move the measure.

Ornstein wasn't buying it. "It would be naive to imagine that this is just because he promised it to some vets," Ornstein said, adding that the strategy "absolutely relates to Frist's larger ambitions."

The issue could become politically awkward back in Washington.

Frist's deputy in the Senate, Republican Whip Mitch McConnell of Kentucky, has been one of the leading opponents of amending the Constitution to ban flag-burning. Frist, who is leaving the Senate in January, has said McConnell is his pick to become the new majority leader.

McConnell, who also attended the conference in Memphis, plans to continue his opposition to the flag-burning amendment, said his spokesman, Robert Steurer.

Critics of the amendment call it a free-speech issue and say lawmakers should have great reservations about altering the Constitution. The Supreme Court has ruled that flag-burning is protected under the First Amendment.

The House approved a measure last June amending the Constitution to ban flag-burning.

A constitutional amendment must be approved by two-thirds of the House and Senate, then ratified by at least 38 state legislatures.

Only 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, extended the right to vote to citizens as young as 18.