The U.S. Conference of Catholic Bishops (USCCB) endorsed Rep. Bart Stupak's (D-Mich.) abortion amendment today, giving the proposal a boost of momentum just hours before if comes up for a vote.

Stupak has been wrangling with his own party over the amendment, which would prevent federal subsidies from going to any insurance plans that cover abortion.

Democratic leaders agreed late last night to allow a vote on Stupak's proposal. The Michigan Democrat had warned that 40 pro-life Democrats would help defeat the bill if their concerns weren't addressed.

The USCCB announced its position in a letter to lawmakers, arguing that Stupak's amendment was consistent with the Hyde Amendment, a long standing policy that prevents federal dollars from going to elective abortions.

"[W]e strongly urge you to vote for the [Stupak proposal] and to support a fair process in the House of Representatives to consider this essential improvement in health care reform legislation," the letter reads.

Republican leaders told their members they will support the amendment. Some observers speculated Republicans might vote against the amendment in the hopes of making the final bill unpalatable to pro-life Democrats.