In a symbolic act, welcomed by gay rights advocates, Gov. Mark Dayton Wednesday vetoed the Legislature's constitutional amendment defining marriage as only a union between one man and one woman.

Constitutional amendments do not require a governor's signature, so the veto has no power. But since the amendment came to him as a bill, he felt the need to make his strong condemnation known.

"I do not have the power to prevent this divisive and destructive constitutional amendment from appearing on the ballot, in November 2012, the Legislature sent it to me in the form of a bill," he wrote in a letter to legislative leaders. "Thus, symbolic as it my be, I am exercising my legal responsibility to either sign or veto it."

He predicted the amendment will fail when it comes before Minnesotans. If that happens, Minnesota voters would be the first voters of dozens of states to reject a gay marriage ban.

"The path of social progress, of human compassion and understanding, would be tragically reversed by this amendment. Minnesotans are better than this. I urge Minnesotans to reject this amendment," he wrote.

Later today, the governor will release a non-symbolic veto of the Legislature's two anti-abortion measures. One of those measures would ban abortion after 20 weeks. The other would ban the state from paying for abortions for low-income women.

The governor is also due soon to act on the Legislature's voter ID measure, which would require voters to present photo identification before casting ballots and make other significant changes to election law.

He said Wednesday that he had met with two lawmakers and the Secretary of State to discuss the measure Wednesday.

The lawmakers -- Sen. Katie Sieben and Rep. Paul Thissen -- and Secretary of State Mark Ritchie are against the measure. Dayton, who has avoided the word veto regarding the election change, said their advice may be "persuasive."

Here's the veto letter about the marriage amendment:

Amendment Veto Letter