Dissidents criticise the leadership of AFL-CIO president John Sweeney

The Teamsters and the Service Employees unions say the AFL-CIO neglected the movement's loss of members and influence in favour of politics.

Another two unions are boycotting the current AFL-CIO convention in Chicago.

Correspondents say the US labour movement now faces one of the biggest splits in its history.

The breakaway unions have already set up a rival organisation.

Service Employees' International is the largest and fastest-growing union in the US, with more than 1.8 million members, while the Teamsters call themselves "the world's most powerful union".

The rebels are among seven dissident unions representing a third of the AFL-CIO's 13m members - and $35m (£20m) in dues.

Experts say a split in US labour could hurt the Democratic party, which generally gets strong union backing.

Simmering tension

The split came at a convention meant to celebrate the 50th anniversary of the merger of the American Federation of Labor and the Congress of Industrial Organizations.

Anna Burger said the AFL-CIO had not done enough to change

AFL-CIO president John Sweeney criticised the rebels at the start of the convention.

"At a time when our corporate and conservative adversaries have created the most powerful anti-worker political machine in the history of our country, a divided movement hurts the hopes of working families for a better life," he said to a standing ovation.

Long-simmering tension between the dissidents - part of a coalition called Change to Win - and AFL-CIO burst into the open on Sunday.

"Today, we have reached a point where our differences have become unresolvable," coalition chair Anna Burger said in a statement on the eve of the convention.

About 1,000 supporters of Mr Sweeney rallied on Sunday under the slogan United to Win, the AFL-CIO said.

The dissident unions are unhappy with Mr Sweeney's leadership. He is expected to win re-election without challenge at the convention.

The US labour movement has long been in decline.

According to government statistics, 12.5% of all US workers - and 8% of private-sector workers - are union members.

In the 1950s and 1960s, about a third of workers were unionised.