Last week, the Supreme Court struck down a provision of the Defense of Marriage Act that denied federal benefits to same-sex married couples. Boxer said federal agencies should be working "expeditiously" to ensure benefits are immediately available.

“All federal agencies should endeavor to provide swift and equal access to programs and benefits for all same-sex couples, regardless of their state of residence, using existing administrative authorities,” Boxer said.

Boxer “applauded” the Social Security Administration (SSA) acting commissioner Carolyn Colvin in a letter Monday, saying she directed field offices to start accepting benefit application from same-sex couples, but the applications will be put on hold until it is determined how to proceed.

 “While I understand the SSA’s review of its legal authorities regarding same-sex couples must be comprehensive and thorough, I encourage you to work as expeditiously as possible for the millions of Americans who await your decisions,” Boxer wrote.

Boxer added that Colvin should alert lawmakers if the SSA needed congressional action to make changes.

“In instances where remedies are not available through executive action and will instead require specific changes to existing law, I urge you to notify Congress immediately so that the legislative process to address these issues can begin,” the letter stated.