WASHINGTON — The Obama administration will launch a lobbying push Tuesday to stop Congress from approving harsh new penalties for Iran, a move the White House warns could sink international negotiations aimed at curbing Tehran's nuclear program.

A bipartisan group of lawmakers, including Sens. Robert Menendez (D-N.J.) and Mark Steven Kirk (R-Ill.), has nearly completed sanctions legislation that it hopes to attach as an amendment to the annual, must-pass defense authorization bill, which could face a vote this week before Congress adjourns for the holidays.

The bipartisan group is "inches from finalizing a deal," according to a senior congressional aide who asked not to be identified because he was not authorized to speak publicly. It's not clear that both the House of Representatives and the Senate will vote to attach the amendment, as is required.

The amendment would seek to reduce Iran's remaining oil revenue — which has been cut by more than half as a result of earlier sanctions — almost to zero within a year after the new sanctions take effect.