CHARLOTTE, N.C. - Unions, traditionally a force at Democratic National Conventions, are largely skipping this year's quadrennial festivities.

Many of Charlotte's local unions are still marching, but their ranks won't be fleshed out by brethren from across the country, who typically converge on Democratic convention cities to volunteer, rally and host policy briefings.

National labor leaders are angry that the Democrats chose to have their convention in a right-to-work state and in a city they say has too few unionized workers.

"There are plenty of other places this convention could have been held where union members would have been involved from start to finish in the preparation, the planning, the work, the set-up, the operation, the tear-down and every aspect of dealing with this convention," said Phil Smith, spokesman for the United Mine Workers of America.

The AFL-CIO is bowing out, too. "We won't be buying skyboxes, hosting events other than the labor delegates meeting or bringing a big staff to the convention," union President Richard Trumka wrote last month in a letter to his union's local leaders.

But, labor leaders say, don't confuse the message of the boycott. Unions still support President Obama and Democratic policy.

"Does that mean unions will abandon Obama in November? Don't bet on it," said Phillip Wilson, president of the Labor Relations Institute, a human resources consulting firm in Broken Arrow, Okla. "Unions will be around, especially in state and local elections, where they feel they have more control over the politicians they help elect."

Some union members, though, are disenchanted with Obama for blocking the Canada-to-Texas Keystone XL pipeline, which would have brought thousands of new construction jobs.

Labor groups also are disappointed in him for not pressing hard enough for the Employee Free Choice Act, which would make it easier for workers to unionize. Some, such as United Mine Workers of America members, oppose new environmental regulations that they say harm the coal mining industry.

No Mine Workers endorsement

In fact, the UMW, which strongly backed Obama in 2008, hasn't decided whether to endorse him for re-election.

The UMW's absence contrasts with Democratic conventions in 2004 and 2008, when it sponsored receptions and briefed state delegations on labor issues in Boston and Denver.

"That's not to say we disrespect the workers in North Carolina who are not union members. We wish they were union members, but the way the laws are in North Carolina it's very difficult for them to become union members without going through intimidation factors by their employers," Smith said.

"We don't think it's right to reward that" by having a convention there, he said.

Other unions though, are firmly behind the president, even as they decry the party's choice of a convention location.

"We are deeply committed to re-elect President Obama and Vice President Biden," Trumka said in his letter.

On Monday, more than 300 people marched in the Charlotte Labor Day Parade, carrying signs, wearing matching shirts and chanting. In contrast to a protest the previous day, the atmosphere was overwhelmingly pro-Obama, family-friendly and generally low-key. The police presence was much lighter.

The Associated Press contributed to this report.