The Obama administration on Friday urged the Supreme Court to strike down a portion of the Defense of Marriage Act (DOMA).

In a brief filed by Solicitor General Donald Verrilli, the administration argues that Section 3 of DOMA, which defines marriage for federal agencies as a heterosexual union, is unconstitutional.

“Section 3 of DOMA violates the fundamental constitutional guarantee of equal protection,” the administration wrote. “The law denies to tens of thousands of same-sex couples who are legally married under state law an array of important federal benefits that are available to legally married opposite-sex couples. Because this discrimination cannot be justified as substantially furthering any important governmental interest, Section 3 is unconstitutional.”

Laws which are based on sexual orientation should face heightened scrutiny, the standard most often used for cases involving a claim of civil rights infringement, the administration said.

The Supreme Court next month will hear oral arguments in the case, Windsor v. United States. An appellate court hearing the case last year struck down DOMA for the first time using heightened scrutiny.

The administration has made similar arguments in the case as it wound its way to the Supreme Court. However, the government has not said whether it will get involved in a second case before the high court related to marriage equality. On Wednesday, President Barack Obama said he was still weighing his options in a challenge to Proposition 8, California's marriage ban.

(Related: Obama reiterates gay marriage support in discussing Prop 8 case.)