Democrats have put off a decision on choosing a 2008 national convention site until early January, hard-pressed to pick between Denver and New York, officials said Tuesday.

Party officials have been negotiating for months with host committees for New York and Denver, but a series of problems with Denver's bid — and a significant cooling of interest from New York Mayor Michael Bloomberg — led Democratic Party Chairman Howard Dean to seek more time to make a decision.

"Chairman Dean is going to make the best decision for the party based on the merits of each city's bid. ... Because of the holiday week, and at the request of both cities, we will announce the convention city in early January," DNC press secretary Stacie Paxton said in a statement.

Denver, which has mounted an enthusiastic campaign to win the convention, has struggled with labor issues, fundraising and logistical challenges such as finding sufficient hotel rooms. Democrats thought Denver had resolved some of its labor problems when Colorado's AFL-CIO approved a resolution last month in support of Denver's convention bid.

But problems suddenly emerged this week when Jim Taylor, head of city's influential stagehand union, refused to sign an agreement promising not to strike if the convention came to Denver.

Debbie Willhite, executive director of Denver's host committee, said a lack of full union support for the city's bid is "probably a deal-breaker" but expressed confidence the matter could be negotiated.

The problems are different in New York, which hosted the 2004 Republican National Convention and eagerly sought the 2008 Democratic gathering as recently as a few months ago. Since then, Bloomberg has committed to several other multimillion-dollar fundraising efforts, including creation of the city's World Trade Center memorial.

While New York's host committee has pledged to raise the money necessary to hold the convention, Bloomberg said Tuesday that the fundraising would be significantly more difficult than he once believed.

"The city can't go on the hook for a convention unless they're reasonably sure they can raise the money," he said, noting that New York had financed the 2004 convention entirely through private fundraising.

"We'd like conventions to come here and spend money and be a net positive for this city, so while it was in the last case because we financed it all privately, I'm not sure we could do that again," he said.

The convention — which is expected to attract 35,000 people, including 4,950 delegates and alternates — will be held from Aug. 25-28 after the Summer Olympics in Beijing.

The Republican National Convention will start just 4 days later, on Sept. 1 in Minneapolis-St. Paul, Minn.

Denver last hosted the Democratic National Convention in 1908, when Democrats nominated William Jennings Bryan in his third unsuccessful effort as the party's standard-bearer. But many Democrats have said the selection of Denver this time would make a powerful statement about the party's recent resurgence in the Rocky Mountain West.

New York has other advantages, including a winning track record with Democrats. The last two Democrats to occupy the Oval Office were first nominated in New York — Jimmy Carter in 1976 and Bill Clinton in 1992.

New York also has several powerful allies, most notably Sen. Hillary Rodham Clinton, the prospective front-runner for the party's presidential nomination. The state's other senator, Chuck Schumer, led the successful effort by Democrats in November's midterm election to retake control of the Senate.