The ban on openly gay US troops will come to an end on Tuesday, 18 years after it was signed into law.

Despite some attempts to derail the repeal, the process is on track.

This week, two powerful Republicans on the House Armed Service Committee wrote to defence secretary Leon Panetta to ask him to “take immediate action to delay the implementation of repeal.”

Rep Buck McKeon and Rep Joe Wilson argued that the Pentagon was unprepared for repeal because the committee has not received copies of all regulation and policy changes due to take place under the change.

A Pentagon statement dismissed their claims, saying that House Armed Services Committee staff were aware of all revisions.

The GOP politicians’ move was seen as a last-ditch attempt to block repeal.

Joe Solmonese, president of the Human Rights Campaign, called the letter a “desperate move by extremist House members”, while Aubrey Sarvis, executive director of the Servicemembers Legal Defense Network, said it was “another example of the hardcore opposition [against repealing the gay ban]“.

The Servicemembers Legal Defense Network has produced a document for LGBT troops which gives advice on attending Pride events, what to do in cases of harassment and whether to come out.

Gay group Log Cabin Republicans has warned that the ban could be reinstated in future as the law has not been declared unconstitutional. They have taken the issue to court.

Dan Woods, a lawyer for the group, said earlier this month: “Several leading Republican presidential candidates have gone on record promising to ‘repeal the repeal’.

“The military could also bypass Congress and enact new regulations, and a new Congress could re-enact DADT [Don't Ask, Don't Tell].”

Mr Wood added that having the law declared unconstitutional could also allow troops fired under the 18-year-old law to claim back pay, reinstatement or a change in discharge status.

Justice Department attorneys say repealing the statute invalidates constitutional challenges.

They have asked the 9th US Circuit Court of Appeals to throw out the case.