WASHINGTON (CNN) -- President Bush will deliver a prime-time speech Wednesday night to put pressure on Congress to pass a $700 billion plan to bail out Wall Street, the White House announced.

Federal Reserve chief Ben Bernanke warned Wednesday that the current Wall Street crisis is the worst the country has faced since the end of World War II and urged Congress to take action on a proposed bailout package.

But members of Congress - including members of Bush's own Republican Party - have expressed skepticism about the plan drafted by Bernanke and Treasury Secretary Henry Paulson.

Bush's speech is due to begin at 9:01 p.m. ET and last just under 15 minutes.

Minutes before the speech was announced, the Democratic leader in the Senate blasted Bush, accusing him of being "absent from what may well be the most important debate on economic policy in a generation."

"Where is President Bush?" Sen. Harry Reid, a Nevada Democrat, demanded on the Senate floor. "President Bush has sent Congress an unprecedented $700 billion bailout proposal - $700 billion straight from the pockets of every single man, woman and child in America.

"It is time for him to explain how his plan, drafted literally under the cover of darkness, will help America weather this storm."