In a move considered unthinkable even a few months ago, congressional leaders have agreed to lift the nation’s 40-year-old ban on oil exports, a historic action that reflects political and economic shifts driven by a boom in U.S. oil drilling.

The measure allowing oil exports is at the center of a deal that Republican leaders announced late Tuesday on spending and tax legislation. However, Democrats haven’t confirmed the agreement. Both the House and Senate still must pass it and President Barack Obama must sign it into law.