Sen. Ben Cardin (D-Md.) was mum Wednesday about how long the Senate's planned all-night session could last, but indicated it could extend past midnight into Thursday.

Democrats are planning the session to pressure Republicans to open debate on the financial regulatory reform bill currently stalled in the Senate.

Asked at a press conference how long Democrats planned to keep the Senate in session, Cardin shot back "you mean, how early?"

During the healthcare debate, Democrats threatened many times to hold all-night sessions, but the only late night sessions took place when votes were taken.

Cardin said that Democrats would offer unanimous consent to move forward with debate, which only requires one senator's objection to block, and that they could make quorum calls to make sure senators stick around.

The Maryland senator framed the strategic move as a response to Republicans' abuse of the filibuster. He complained that the GOP is blocking a vote to open debate, not a motion to move to a final vote on the bill. He said that the GOP wants to add provisions behind closed doors, not out in the open.

"They want to weaken the bill," he said. "That's the reason we plan to stay here tonight...we are going to sty here and do this work."

Cardin was asked repeatedly how long the Senate would stay in session, but he ducked, saying "we plan to stay in session."