WASHINGTON (AP) – Senate Democrats say they will block action on President Barack Obama’s trade initiatives unless Republicans make more concessions.

Aides to pro-trade Democrats said they wouldn’t accept Republican restrictions on a trade package scheduled for a key procedural vote Tuesday. They appeared to have enough votes to block further debate and action for now.

Obama’s trade allies need 60 votes to proceed. Republicans hold 54 of the Senate’s 100 seats.

A Senate setback Tuesday would be embarrassing but not necessarily fatal to Obama’s bid for “fast track” authority to negotiate trade deals. He could try later in the Senate, or ask the House to move first.

Under fast track, Congress can reject or ratify trade proposals, but not amend them.