NEW YORK -- A weekend of St. Patrick's Day revelry and tensions over the exclusion of gays in some of the celebrations culminated Monday in New York, where the world's largest parade celebrating Irish heritage stepped off without the city's new mayor and Guinness beer amid a dispute over whether participants can carry pro-gay signs.

The parade of kilted Irish-Americans and bagpipers set off on a cold, grey morning. Hundreds of thousands of spectators lined Fifth Avenue, but the shivering, bundled up crowd was only about half as thick as in previous years. Revelers also gathered in Dublin and in Savannah, Georgia, for green-themed celebrations.

De Blasio held the traditional St. Patrick's Day breakfast at Gracie Mansion with the Irish prime minister, Enda Kenny, but boycotted the parade because organizers said marchers were not allowed to carry gay-friendly signs or identify themselves as lesbian, gay, bisexual or transgender.

Roman Catholic Cardinal Timothy Dolan, who greeted passing dignitaries in front of St. Patrick's Cathedral wearing a woolen Irish cap over his red cardinal's skull cap, said he supports the participation of individual gays and hoped St. Patrick's Day could be a day of unity and joy.

"I know that there are thousands and thousands of gay people marching in this parade," he said. "I know it. And I'm glad they are."

Police Commissioner William Bratton marched with a contingent of uniformed officers. Gay activists protesting the exclusion of official LGBT groups held a news conference before the march to say they didn't think the NYPD officers should participate in uniform.

About two dozen gay rights advocates protested the parade holding placards high enough for marchers to see.

"If Danny Boy were gay, would he be welcome today?" read one.

On Fifth Avenue, Richard Lynch joined the protest lineup wearing a Guy Fawkes mask, which was popular among members of the Occupy Wall Street movement. He said de Blasio should have ordered the police commissioner not to march.

"This was a big mistake," Lynch said. "It says the mayor isn't serious about LGBT inclusion in this parade."

Across the Atlantic in the land that inspired St. Patrick's Day, an estimated 400,000 tourists and locals packed the centre of Dublin for Ireland's major parade. The hour-long procession featured loads of wit, brightly colored costumes and dancers, including from Ireland's gay community -- and nobody had a public word to say about it.

For the second year running, the parade included groups from Ireland's gay rights groups, Dublin Pride and BeLonG To. Gay groups are a big part of the Dublin community dance groups, which wear flamboyant outfits and feature in each year's Dublin parade.

Boston's new mayor, Martin Walsh, opted out of his city's parade Sunday after talks broke down that would have allowed a gay veterans group to march.

Guinness beer abruptly dropped its sponsorship of New York's parade on Sunday over the controversy. The Dublin-based company has pulled sponsorship assets, including on-air presence, parade participation and any promotional materials that weren't already printed, although the beer maker had already made a payment to parade organizers, spokeswoman Alix Dunn said.

Other beer companies earlier joined the boycotts, with Sam Adams withdrawing its sponsorship of Boston's parade and Heineken following suit in New York. That leaves Ford as the last remaining major sponsor of the Manhattan parade.

De Blasio's decision to skip the parade underscores lingering political tensions over gay rights issues in the United States. Kenny, however, refused to be sidelined, saying he'd join the procession Monday in Manhattan because the holiday is about Irishness, not sexuality.

Kenny, Ireland's head of government, on Sunday became the first Irish prime minister to attend Boston's annual St. Patrick's Day breakfast. He has resisted pressure, in both Ireland and America, to support the gay rights lobby's demand to have equal rights to participate in parades on St. Patrick's Day.

De Blasio, in one of the first major events that Gracie Mansion has hosted under the new mayor, addressed several hundred people at the breakfast, many of Irish descent.

Sporting a green tie, de Blasio, who is not Irish, recalled his roots growing up in Massachusetts, living in the congressional district once represented by Irish-Americans John F. Kennedy and Tip O'Neill.

He said in a toast that New York is a "city of immigrants" and residents "never forget" where they came from.

Rain didn't stop the huge St. Patrick's Day celebration in Savannah, Georgia, though fewer revelers lined Lafayette Square nearing the beginning of the city's parade route. Thinner crowds left plenty of room for umbrellas and party tents as the 190-year-old parade stepped off under rainy skies in Georgia's oldest city.

In Ireland, St. Patrick's Day provides the launch of the country's annual push for tourism, a big part of the rural economy. Virtually the entire Irish government left the Emerald Isle for the holiday. Of the government's 28 ministers, 27 are overseas, seeking to boost economic and cultural ties from Beijing to Buenos Aires.

"To Irish people by birth or descent, wherever they may be in the world, and to those who simply consider themselves to be friends of Ireland, I wish each and every one of you a happy, peaceful and authentically Irish St. Patrick's Day," Irish President Michael D. Higgins, the ceremonial head of state and guest of honour at Monday's parade in Dublin, said in a statement.

New York's parade, a tradition that predates the city itself, draws more than 1 million spectators and about 200,000 participants every March 17. It has long been a mandatory stop on the city's political trail, and includes marching bands, traditional Irish dancers and thousands of uniformed city workers.

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Associated Press writers Verena Dobnik in New York, Shawn Pogatchnik in Dublin and Russ Bynum in Savannah, Georgia, contributed to this report.