Many congressional Republicans are advocating a go-slow approach to President George W. Bush's call for a constitutional amendment banning gay marriages.

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House Majority Leader Tom DeLay, a Republican from Texas, said he appreciates the president's "moral leadership" on the issue, but expressed caution about moving too quickly toward a constitutional solution.

While some Republicans urged swift approval of the amendment, others say changing the Constitution should be a "last resort" on any issue.

House Minority Leader Nancy Pelosi, a Democrat who represents San Francisco, vowed to fight any amendment. She said a constitutional amendment has never been used to discriminate against a group of people, adding, "We must not start now."

California Rep. Bob Filner called the president's move a clear case of "wedge politics" designed to divide the country.

Amending the Constitution is not quick or simple. A two-thirds majority of both the House and Senate must pass an amendment, which is then sent to the states for ratification. It must be approved by three-fourths, or at least 38 of the 50 states. (Learn more about amendments.)

Don't Blame San Francisco

San Francisco Mayor Gavin Newsom said Bush is being less than truthful about why proposed the ban.

The president said the recent flurry of same-sex weddings in San Francisco was a factor in his decision. But Newsom said Bush intended to seek a ban long before the gay weddings began taking place.

The president specifically pointed to Newsom's Feb. 12 decision that has allowed more than 3,200 same-sex couples to marry with the city's blessing, possibly in violation of California state law.

Bush also cited a Massachusetts Supreme Court ruling that has cleared the way for gay couples to wed in that state beginning in May. That prompted the Massachusetts legislature to attempt to craft a constitutional amendment defining marriage.

Newsom called the way Bush chose to cloak his endorsement shameful and cowardly.

As Newsom defended the city's policy and more couples exchanged vows at City Hall Tuesday, Bush's announcement received lukewarm reactions from some California Republican leaders.