Amsterdam ? The mayor of Amsterdam presided over the weddings of five American-Dutch gay, lesbian and transgender couples on a boat during the city’s Gay Pride festival Saturday, challenging the United States to legalize gay marriage as well.

Mayor Job Cohen also performed the first weddings in the Netherlands after the country began allowing same-sex marriages in 2001.

“We’ve come really far, farther than we ever thought was possible in just a few years,” Cohen said in an interview between ceremonies. “There’s still a lot to do, that’s the message.”

Each marriage Saturday included one partner from New York and one from the Netherlands.

The festival attracts hundreds of thousands of gay rights supporters, who dance on packed streets in the city center and watch colorful boat-floats parade down the city’s ancient canals.

The marriages were also part of celebrations of the 400th anniversary of New York-Netherlands ties.

Deputy Mayor Carolien Gehrels said New York and Amsterdam are a natural fit, given their “shared values of tolerance, creativity and a spirit of commerce.”

Gehrels, who is married to another Dutch woman, said gay marriage is “a human right.”

Saturday’s marriages may be valid in New York — though they could not have legally been performed there.

Governor David Paterson has ordered that gay marriages approved in other jurisdictions be recognized by the state. U.S. federal law defines marriage as exclusively between a man and a woman.

Ira Siff, a New Yorker who married his Dutch partner Hans Pieter Herman on Saturday, said he believed it was a matter of time before people in New York will able to marry whomever they want.

“We’re the most liberal, advanced state in the United States; it should be happening there now,” he said.

“I imagine it will take a while because there are always factions in the states who confuse religion and government. That’s weird because of course the U.S. was formed to separate those two things.”

A solid majority of the Dutch population now supports gay marriage, polls show, and the topic is considered unremarkable.

But a University of Amsterdam study last year found that attitudes against homosexuality are still strong in the Netherlands and anti-gay violence usually goes unreported.

The study, titled “As Long As They Keep Away From Me,” concluded that the tolerance professed by many Dutch is only a veneer: gay men especially are accepted only as long as they don’t display stereotypically gay behavior.

Police say about 70 gay-bashing attacks a year are reported in Amsterdam, a city of 750,000.

Friday night, vandals painted the words “Homos Go To Hell” in large letters across a bridge where the boat parade was to pass.

Frank van Dalen, the head of the organization that organizes the festival, removed the graffiti and shrugged off the incident. He estimated more than half a million people turned out to watch the parade, a record.

“Today we’re having a party and we are proud,” he said via Twitter.