Republican and Democratic senators have reached a deal on a scaled-down bill to help 9/11 first responders who became sick from having worked in the dust of the World Trade Center.

Congressional aides close to the negotiations tell The Associated Press that the deal calls for providing up to $4 billion in health care and economic aid over five years to first responders and survivors of the Sept. 11, 2001, terrorism attacks.

The aides — three Democratic and one Republican — verified the deal Wednesday but said they couldn't talk about it openly.

The measure is about $2 billion less than the bill proposed earlier this week by Democratic Sens. Chuck Schumer and Kirsten Gillibrand of New York.

Both the Senate and the House were expected to vote on the measure later Wednesday.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

The Senate is headed for a key test vote on a bill that would provide up $6.2 billion to aid people who became sick after being exposed to toxins at the World Trade Center ruins.

Bill supporters say they're confident they have the 60 votes needed to prevail on the vote expected Wednesday. But they worry that Republicans who oppose the measure could try to stall a final vote as the holidays near and Congress' lame duck session winds down.

The bill would provide medical and economic benefits over 10 years to survivors and responders to the Sept. 11, 2001, attacks.

It also would have to be approved by the House. New York lawmakers are pressing the House to remain in session for the vote.