The U.S. Supreme Court is due to take another look today at whether it should review the constitutionality of Proposition 8, California's voter-approved ban on same-sex marriage.

The court announced Monday morning that an appeal by the sponsors of Proposition 8 has been put on the agenda for the justices' private conference on Friday, along with several other cases concerning the federal Defense of Marriage Act.

The announcement came after the court earlier this morning issued no orders either granting or denying review of those cases.

A possible order by the court had been expected for Monday's order list because the marriage cases were also on the agenda of the court's conference last Friday.

The court has no deadline for acting on the cases, however.

This Friday will be the fourth time the marriage cases have been placed on the agenda for the nine justices' internal conference.

Orders resulting from this week's conference would normally be issued either Friday afternoon or next Monday morning.

The sponsors of Proposition 8 and their committee, Protect Marriage, are appealing a decision in which the 9th U.S. Circuit Court of Appeals found the voter initiative unconstitutional.

The lower court ruling has been put on hold and Proposition 8 has remained in effect during the appeal.

The Supreme Court grants review of only a small percentage of the cases appealed to it.

If it denies review of the Proposition 8 appeal, the 9th Circuit ruling will go into effect and gay and lesbian weddings could resume in California as soon as the 9th Circuit issues a mandate.

Lawyers for two couples who challenged Proposition 8 in a federal civil rights lawsuit have said the mandate could be issued within two or three days, clearing the way for same-sex weddings.

If the Supreme Court grants review of the case, it would be expected to hear arguments sometime this spring and issue a decision by the end of June.

In the event the high court denies the appeal, San Francisco and Los Angeles County have asked the 9th Circuit to provide 24 hours notice before issuing the mandate so county clerks can prepare for an expected rush of requests for marriage licenses.

Proposition 8, providing that "only marriage between a man and a woman is valid or recognized in California," was enacted by voters as a state

constitutional amendment in November 2008.

Its sponsors have argued that California voters were entitled to choose a traditional definition of marriage and that each state, acting through its legislature or voters, should be allowed to set its own marriage laws.

If the 9th Circuit ruling is left in place, it would apply only to California because the decision was based on narrow grounds.

The appeals court said by a 2-1 vote in February that because same-sex marriage was legal in California for several months in 2008 before Proposition 8 was passed, it would be unconstitutional to deprive gays and lesbians of an existing right.

Nine states and the District of Columbia now permit same-sex marriage, including three states -- Maine, Maryland and Washington -- in which voters approved the unions in the Nov. 6 election.

The other states are Connecticut, Iowa, Massachusetts, New Hampshire, New York and Vermont.

The federal Defense of Marriage Act of 1996, known as DOMA, includes a provision barring the U.S. government from recognizing same-sex marriages for the purposes of federal benefits and tax advantages even when the marriage has taken place in a state allowing such unions.

That section of the law has been struck down by U.S. appeals courts in Boston and New York and by several federal trial judges around the nation, including U.S. District Judge Jeffrey White in San Francisco.

White acted in the case of a Karen Golinski, a federal appeals court employee who wants to enroll her wife, whom she married in California in 2008, in the court's health insurance program.

Supreme Court appeals in several of those cases, including the Golinski case, have been filed by the Republican leadership of the House of Representatives.

The Obama administration announced last year that it now considers that provision of the law unconstitutional and will no longer defend it in

court.

Another section of DOMA, which is not at issue in the appeals, allows individual states to refuse to recognize marriages that were legally performed in other states.