The party’s Platform Drafting Committee agreed, unanimously, to approve the language at a meeting this weekend in Minneapolis.
A source in the meeting said the decision was “not controversial.”
The language will not become official until the party’s full Platform Committee meets Aug. 10 in Detroit.
The effort to include gay marriage in the platform gained increased momentum after President Barack Obama announced in May that his views on the issue had changed to support legalization.
“I don’t think that we had any issues that were controversial,” one member of the committee said Monday. “I think we were pretty much in sync and in agreement with where we ended up.”