Top officials in the US are pushing the Pentagon to insist that state National Guards process benefits for same-sex couples in line with the a recent directive from the Defense Department to treat married same-sex service members equally.

Chairman of the Senate Armed Services Committee, Carl Levin, a Republican, and Representative Adam Smith, a Democrat, and the ranking member of the House Armed Services Committee penned a letter this week urging Defense Secretary Chuck Hagel to act on the issue.

Last month four US state National Guards  said they would not follow the directive, all citing their state-wide bans on equal marriage. National Guard members were able to go to federal facilities, those states said.

Levin and Smith wrote: “We urge you to issue further guidance on this matter, reaffirming that all married couples must be treated equally.”

The issue has caused conflict between states unwilling to issue benefit cards to same-sex couples, and the Obama administration.

This week’s letter, however, argued that the National Guards must process the benefit application “because they are funded in large part by federal tax dollars.” In it, the pair noted the US Supreme Court’s July strike-down of the Defense of Marriage Act, which opened over 1,100 benefits to same-sex couples.

The American Military Partners Association on Thursday said: “This discrimination by the national guard in a few states has gone unaddressed for too long and is only getting worse,” the group’s president, Stephen Peters said in a statement. “These service members and their families deserve better than to be treated poorly by state governors trying to score political points. We again call on the Secretary of Defense for quick and decisive action.”

The National Guard in the US state of South Carolina earlier this week announced that it was directing benefit applications to federal installations to avoid a conflict with a law banning equal marriage in the state.