"Today the Senate will vote on a extreme ideological amendment to the transportation bill," said Reid. "[T]his amendment has no place on a transportation bill."

The amendment would reverse the Obama administration's ruling that health plans must offer contraception coverage, even those offered by church-related organizations. A vote on the amendment should begin just after 11 a.m. on Thursday. 

Early last month Reid refused to allow a vote on the amendment, which could create perils for Democrats on the campaign trail later this year. Republicans made it clear, however, that without a vote they would prevent progress on the underlying highway bill, which Democrats say would create or save about 2.8 million jobs.