(CNN) - CNN has learned the 1.9 million-member Service Employees International Union is poised to endorse Sen. Barack Obama for President.
Three sources familiar with the deliberations said union leaders met via conference call Thursday to deliberate on the endorsement issue. These sources, speaking to CNN on condition of anonymity, said Obama was the overwhelming choice of the union's state and national leadership.
Barring an unexpected complication, the endorsement could be announced as early as Friday morning, the sources said.
It would be a significant boost for Obama, including in the coming major primary battlegrounds of Ohio, Texas and Pennsylvania.
Thursday afternoon, Obama received another major labor endorsement likely to help in those delegate rich-states, when the 1.3-million member United Food and Commercial Workers Union decided to back his presidential bid.
–CNN Chief National Correspondent John King