The United States' largest labor federation will mobilize as many as 400-thousand volunteers to aid in U.S. President Barack Obama's reelection effort.

AFL-CIO President Richard Trumka announced his organization’s support for Obama on Tuesday, saying that the president has helped save thousands of jobs in the U.S.

The anticipated volunteer force represents roughly three percent of the federation's 12 million affiliate union members.

Trumka said that Republican presidential hopeful Mitt Romney is depending on the patronage of wealthy supporters, and the U.S. economy will slip back into a slump if Romney becomes president.

The AFL-CIO publicly announced in March its unanimous decision to endorse Obama in the presidential race, noting the president’s achievements such as strengthened financial regulations on Wall Street and health insurance reforms.