Celebrities including Jane Lynch, Ellen DeGeneres and Anne Hathaway are joining to urge President Obama to support gay marriage, the Los Angeles Times reported.

Freedom to Marry kicked off the Say I Do campaign on Monday with a letter to Obama asking the president for clarity on the topic.

Signers include actors Eric McCormack, Martin Sheen, Lily Tomlin, Jane Wagner and Portia DeGeneres, musicians Melissa Etheridge, Mya and Rufus Wainwright, playwright Tony Kusher and studio executive David Geffen. Also included are social media titans Jack Dorsey, creator of Twitter, and Chris Hughes, co-creator of Facebook, and NFL athletes Brendon Ayanbadejo of the Baltimore Ravens and Scott Fujita of the Cleveland Browns.

Lynch, who married her wife Lara Embry in a ceremony last year in Massachusetts, wrote: “My wife and I were married in May of 2010, and I can say without a doubt that marriage matters.”

Chat show host Ellen DeGeneres married her wife, Portia DeGeneres, formerly known as Portia de Rossi, in California in 2008. Chris Hughes is engaged to marry gay rights advocate Sean Eldridge.

The letter reads: “In law, in love, in life, marriage says 'we are family' in a way that nothing else does. Marriage is the coming together of two lives, marked by a public promise of love and responsibility in front of friends and family. And marriage brings not only public respect and personal significance, but also a safety net of legal protections, rights, and responsibilities for which there is no substitute.”

Obama has said he personally supports government recognition of gay unions but not marriage, a position he recently said he “wrestles” with.