A bill to legalize same-sex marriage, which would make Delaware the 10th US state to extend marriage rights to gay and lesbian couples, was due to be announced by Governor Jack Markell on Thursday.
Markell, a Democrat, was to make the announcement at an afternoon press conference, his office said. He was to be joined by state Senate President Pro Tempore Patricia Blevins, House Speaker Pete Schwartzkopf and Attorney General Beau Biden.
Delaware currently allows same-sex couples to enter into civil unions.
Nine states and the District of Columbia allow same-sex marriage: Connecticut, Iowa, Maine, Maryland, Massachusetts, New Hampshire, New York, Vermont and Washington.
The US Supreme Court is considering a legal challenge to a 1996 law that restricts federal recognition of marriage to heterosexual couples.