All 42 Senate Republicans have threatened to block repeal of “Don't Ask, Don't Tell,” the 17-year-old law that bans gay and bisexual troops from serving openly, unless Democrats agree to move on tax issues, the AP reported.

In a letter addressed to Senate Majority Leader Harry Reid, Republicans vowed to block any measure until the chamber has “acted to fund the government and we have prevented the tax increase that is currently awaiting all taxpayers.”

“With little time left in this Congressional session, legislative scheduling should be focused on these critical priorities. While there are other items that might ultimately be worthy of the Senate's attention, we cannot agree to prioritize any matters above the critical issues of funding the government and preventing a job-killing tax hike,” the GOP senators wrote, referring to the imminent end of the Bush-era tax cuts.

The threat, if carried out, means the end of the road for repeal of the law that has ended the military careers of over 13,000 service members for the near term.

Reid blasted the GOP caucus for backing an “obstruct and delay” strategy.

“Republicans have simply put in writing the political strategy they have pursued over the last two years: obstruct and delay critical help for struggling Americans, and then blame others for the problems they refuse to solve,” Reid said in a statement on Wednesday. “This strategy is very cynical but very obvious and transparent.”

Aubrey Sarvis, executive director of the Servicemembers Legal Defense Network (SLDN), the largest group lobbying for repeal of the Clinton-era law, also chided Republicans.

“The Republican caucus that has expressed strong support for a vote on extending the Bush-era tax cuts should be as equally unified in support of a vote in the lame-duck session on the nation's defense bill, the very bill which provides for our security and the well being of service members who defend us every day,” Sarvis said in a statement.

Ultimatum or not, a Senate panel is expected on Thursday to begin two days' worth of testimony on a Pentagon report on how to repeal the law.