The AFL-CIO is on the verge of endorsing Barack Obama for president.

The leaders of the nation's largest labor organization started voting Tuesday on whether to endorse Obama's presidential nomination. Voting, which is being done by fax, is expected to end on Thursday.

Obama's name is the only one on the ballot.

Officials representing two-thirds of the AFL-CIO's 8 million union members must support Obama for him to get the endorsement.

The AFL-CIO's endorsement is virtually certain now that Obama is the presumptive Democratic presidential nominee. He received an enthusiastic reception from labor leaders while meeting with the AFL-CIO at their Washington headquarters last week.