Keller wrote in a letter to the borough council that he did not want to breach his official duties as mayor by officiating at a wedding that might not be legal, a stance unpopular with a number of local residents.
He maintained during the public outcry that he supported same-sex marriage, a position he reiterated in his letter to Corbett.
"While I will obey the laws of our land as mayor of New Hope Borough," he wrote, "I hope in the near future this law will change so I can obey the law and do what is right in my heart."
He also called the decision to decline the couple's request "heartbreaking."
Marcus Saitschenko, whose request Keller denied, said Friday that "I don't think [Keller] was as heartbroken as I was when I was discriminated against," but added: "His letter to the governor is a fair effort to make amends, and I do appreciate that gesture."
Geri Delavich, a Democratic borough council member who criticized Keller's decision last week, said that while she thought the letter was "more a reaction than it is taking a proactive stance," she was pleased that "we all agree that marriage equality is good and something that needs to happen."
Delavich's Democratic council colleague, Sheryl Keiser, said, "I'm glad that he's supporting equality," which the "council has supported for many years."
Nils Frederiksen, spokesman for the state Office of General Counsel, said that Corbett had not yet read the letter, but that "the governor certainly appreciates the mayor's interest, and he will review the letter."
Saitschenko said that he and his partner were still searching for a local official to oversee their wedding, and that they had asked several, including Mayor Nutter.
Mark McDonald, Nutter's spokesman, said the mayor's office was "in a holding pattern" with regard to such requests until after a case challenging the state's marriage law had run its course.
McDonald said he was unaware of any requests for the mayor to officiate at a same-sex wedding.
Contact Chris Palmer, 609-217-8305, firstname.lastname@example.org, or follow on Twitter, @cs_palmer.