Neil Patrick Harris, Robert De Niro and Julianne Moore were among the celebrities attending the Human Rights Campaign's (HRC) Americans for Marriage Equality campaign launch event.

Monday's New York City party was hosted by the Calvin Klein Collection's creative team of Francisco Costa and Italo Zucchelli.

Americans for Marriage Equality is an HRC video campaign that features celebrities, politicians and athletes urging Americans to support marriage equality. It is modeled after the group's highly successful New Yorkers for Marriage Equality campaign.

Also attending the event were New York Rangers left wing Sean Avery, comedian Jerry Seinfeld, New York City Council Speaker Christine Quinn, Vogue editor-in-chief Anna Wintour and singer Courtney Love.

Several of the celebrities in attendance, including Avery, Wintour and Moore, participated in HRC's campaign to win gay marriage in New York.

HRC's Americans for Marriage Equality campaign premiered on October 31 with a video featuring Julian Bond, chairman emeritus of the National Association for the Advancement of Colored People (NAACP). Actor John Leguizamo and playwright Katori Hall have also recorded videos for the campaign.