By Keith Coffman

DENVER (Reuters) - The Colorado attorney general's office filed a motion in federal court on Wednesday, seeking an injunction to suspend same-sex marriage litigation in the state until the U.S. Supreme Court ultimately rules on the issue.

Last week the 10th U.S. Circuit Court of Appeals in Denver ruled that neighboring Utah cannot stop gay couples from being wed, but stayed the order until the Supreme Court decides.

Since then the clerk in Colorado's Boulder County has issued nearly 100 same-sex marriage licenses, and has rejected requests by the attorney general's office to halt the practice.

In Wednesday's motion, filed in U.S. District Court in Denver, the attorney general's office said that without an injunction the legal uncertainty would "invite a race to the clerks' office" by couples seeking licenses before the issue is resolved by higher courts.

On Tuesday, six couples filed suit in Denver federal court seeking to overturn Colorado's constitutional amendment that defines marriage as a union between a man and a woman. The state does permit same-sex civil unions.

Dan Domenico, Colorado's solicitor general, said a temporary halt would be beneficial to all sides.

"We hope and believe that if granted, today's motion will help end the divisive, costly, and now unnecessary litigation regarding same-sex marriage in Colorado," he said in a statement.

The attorney general's office will file similar motions in state court, where gay couples have also filed lawsuits seeking to overturn the ban, it said.

In Boulder, the elected county clerk has said same-sex licenses are "legal and just," and that she will continue to issue them. [ID:nL2N0PC1ZB]

Attorney General John Suthers has threatened to take unspecified legal action against her, arguing that Colorado's ban on gay marriage remains in place because the 10th Circuit stayed its verdict on Utah.

In a letter sent to the attorney general's office on Wednesday, Boulder County Attorney Ben Pearlman said the county will continue issuing marriage licenses to gays because "the (10th Circuit) stay is too fragile a shield to hide behind."

(Reporting by Keith Coffman; Editing by Daniel Wallis and Ken Wills)

[Same sex marriage via Shutterstock]