President Barack Obama will throw his weight behind legislative bids to reform healthcare on Tuesday in his fourth White House press conference since taking office.

Legislation on two of Obama's signature issues -- covering 46 million Americans who do not have health insurance and capping carbon dioxide pollution from major industries -- is currently moving through the U.S. Congress.

But both bills face obstacles. Lawmakers are worried about the $1 trillion healthcare reform is expected to cost over the next 10 years, while the climate bill's chances of passage, though more positive in the House of Representatives, are less clear in the Senate.

Obama hopes to shore up support on both issues while addressing international crises including unrest in Iran following contested presidential elections there and tension on the Korean peninsula.

He is scheduled to make an opening statement at 12:30 p.m. EDT in the White House Rose Garden and then take questions from reporters for about an hour.

A newly released Washington Post/ABC News poll showed only about half of Americans believe the president's $787 billion stimulus package will boost the economy.