U.S. presumptive presidential nominee Barack Obama's campaign wooed women voters on Tuesday by promising economic relief policies for working women as Vice President candidate Joe Biden made his public debut at the national convention.

"Working women are struggling," Michelle Obama told the roundtable meeting with working women across the country. "They are asked to shoulder an enormous burden, but they are not given enough resources."

Michelle Obama, wife of US Senator Barack Obama, waves as she arrives at the podium to speak at the 2008 Democratic National Convention in Denver Aug. 25, 2008. U.S. Senator Barack Obama (D-IL) is expected to accept the Democratic presidential nomination at the convention on Aug. 28.[Xinhua/Reuters Photo]

Citing Obama's mum, who had to give up college to raise children alone, and Biden, who had been taking care of his two sons for five years after his ex-wife was killed in a car accident, Michelle underscored that the two candidates understand challenges facing the U.S. working women.

"As President and Vice President, Barack and Joe will change Washington, so that instead of just talking about family values, we actually have policies that value families," she said.

Michelle referred to the "Obama-Biden Plan to Support Working Women and Families," a program released on Tuesday that outlines practical ways "to lighten the load that working women carry everyday."

As the expansion of the current Family and Medical Leave Act, the 12-page plan is aimed at assuring working women with time off to care for a baby or elder parents and requiring employers to provide workers with paid on sick days, among others.

Biden accused President George W. Bush's government of giving working women and their families eight tough years and promised to fix the damages if Obama is elected the next president.

"We will also stand with women and help working families on every issue from jobs and wages to health care and retirement savings," he said.

With a little more than two months to go before the November election day, Obama is still struggling to win over the blue-collar and women voters who used to be the supporter base for his formal rival, Hillary Rodham Clinton.

Recent polls showed that about 27 percent of Clinton's supporters said they would vote for Republican presidential candidate John McCain in November, and about 20 percent others remained undecided.

The four-day Democratic National Convention began on Monday through Thursday in Denver, Colorado, where Obama and Biden will accept their nominations.