People.com: Cynthia Nixon announced her engagement to girlfriend Christine Marinoni at a Sunday rally in New York to support same-sex marriage, reports Access Hollywood.

At the rally, which also attracted Gov. David A. Paterson and Mayor Michael Bloomberg, the Sex and the City actress, 43, flashed the diamond engagement ring Marinoni, 42, gave her and said, "It's time already," reports New York's Daily News.

Nixon and Marinoni began dating in 2004, following the actress's 2003 split from her companion of 16 years, photographer Danny Mozes, with whom she has two children: Samantha, 12, and Charles, 6. "When I first started dating my girlfriend and people got wind of it, I said, 'Yes, that's true,' " Nixon told PEOPLE in May 2008.

About that same time, with California having legalized gay marriage (a law subsequently struck down in the November 2008 election), Nixon told the News, "In an ideal world, we'd like to in New York, when it becomes legalized."

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