The lengthy fight to allow gay marriage across the United States may soon be at an end with the Supreme Court set on Tuesday to consider whether same-sex couples have a constitutional right to wed.

Experts said it seems inevitable that the nation's top court will recognize gay marriage, already legal in 37 of the country's 50 states and in the capital, Washington. A ruling is expected at the end of June.

"Marriage equality has advanced with remarkable speed through the states," said constitutional law professor Steven Schwinn of the John Marshall Law School in Chicago. "In effect, the Supreme Court allowed same-sex marriages to move forward in those jurisdictions, making it all the more difficult to roll back marriage equality now."