The chairman of the Joint Chiefs also said in an interview with the Chicago Tribune: "I believe that homosexual acts between individuals are immoral and that we should not condone immoral acts. I do not believe the United States is well-served by a policy that says it is OK to be immoral in any way."
Lawmakers of both parties criticized the remarks, but Brownback's letter called the criticism "both unfair and unfortunate."
"We should not expect someone as qualified, accomplished and articulate as General Pace to lack personal views on important moral issues," Brownback said. "In fact, we should expect that anyone entrusted with such great responsibility will have strong moral views."
Asked whether he agreed with Pace's comments, Brownback said: "I do not believe being a homosexual is immoral, but I do believe homosexual acts are. I'm a Catholic and the church has clear teachings on this."
Democratic candidates Hillary Rodham Clinton and Barack Obama initially tried to sidestep the issue when asked about it this week, but both sought to clarify their opposition to Pace's comments on Thursday.
Obama did not directly answer on Wednesday when asked if same-sex relationships were immoral, Newsday reported. Obama issued a statement on Thursday, saying, "I do not agree with General Pace that homosexuality is immoral. Attempts to divide people like this have consumed too much of our politics over the past six years."
Clinton told ABC News Wednesday that it's for "others to conclude" whether homosexuality is immoral. On Thursday, she put out a statement saying that she'd heard from gay friends who said her answer sounded evasive.
"I should have echoed my colleague Senator John Warner (news, bio, voting record)'s statement forcefully stating that homosexuality is not immoral because that is what I believe," her statement said.
Meanwhile, Democratic hopeful Bill Richardson called Pace's remarks "unfortunate" and said the Bush administration should reject them, adding that he would push Congress to repeal military's "don't ask, don't tell policy" in which gay service members are required to keep their sexual orientation private.