A Kentucky county clerk who had been jailed for refusing to issue marriage licenses to same-sex couples secretly met Pope Francis in a move that disappointed many liberal Catholics and encouraged officials who support her stance.

The meeting with Rowan County Clerk Kim Davis, and comments by the pope on Monday, may spur action by local officials across the United States who have refused to issue marriage licenses to gay couples since the US Supreme Court's June decision to legalise same-sex marriage in all 50 states.

Mat Staver, an attorney for Davis and founder of Liberty Counsel, a law firm that champions conservative Christian causes, told Reuters the meeting was not about sending a message to other clerks or judges who have been unwilling to issue marriage licenses for same-sex couples.

“It was really a meeting between the Pope and Kim Davis and her husband Joe to encourage her,” he said. "It was an amazing opportunity for her to meet the Pope, and for him to be able to stand beside another Christian and to encourage another person who exercised her faith and went to jail for it.”

Staver would not say whether the Vatican or Davis’s representatives had initiated contact about a meeting.

But the meeting angered gay activists and came as a frustrating letdown for gay and other liberal American Catholics, many of whom had been encouraged by an earlier remark by Pope Francis that "If someone is gay and searches for the Lord and has good will, who am I to judge?"

The comment was widely interpreted as a signal that the Church’s hardline stance on homosexuality was softening, a perception that the pope said little to change during his US visit.

According to a new Ipsos/Reuters online poll, 73 percent of respondents said they strongly agreed or agreed somewhat with the pope's statement.

"The news that Pope Francis met privately ... with Kim Davis throws a wet blanket on the good will that the pontiff had garnered during his US visit," Francis DeBernardo, executive director of gay and lesbian Catholic advocacy group New Ways Ministry, said in an emailed statement.

"Pope Francis needs to state clearly where he stands in regard to the inclusion of LGBT people in the church and society."

Still, Pope Francis is enjoying strong approval ratings from Americans of all political stripes, according to the poll, conducted Sept. 21-28, before the meeting with Davis was disclosed. Some 60 percent said they had a favorable opinion of the pontiff while only 10 percent viewed him unfavorably.

One respondent, 67-year-old Catholic Judy Fitzpatrick, said the meeting did not change her favorable opinion about the pope, even though she thinks Davis should step down as county clerk if she can't abide by the law.

"Any time you get people talking and meeting and listening, even if they don't agree, as long as there is a dialogue, I think we are better as a nation," said Fitzpatrick, who describes herself as a moderate Republican.

Davis and her husband met the pope on Thursday during the Washington leg of his US visit, she and her lawyer said. The Vatican confirmed the meeting. Davis could not be reached for comment.

"He told me before he left ... 'Stay strong.' That was a great encouragement," Davis told ABC, saying that her meeting with Pope Francis "kind of validates everything."

As the pope returned from his 10-day trip to the United States and Cuba on Monday, he said government officials had a "human right" to refuse to discharge a duty if they felt it violated their conscience.

In Texas, Alabama and elsewhere a number of clerks and judges have stated their opposition to gay marriage and have mounted roadblocks to such unions.

Alabama Probate Judge Nick Williams, who has refused for months to issue any marriage licenses at all in Washington County while courts sort out a maze of lawsuits and orders, said he was inspired by Davis’ meeting with the Pope.

“I’d say the Pope has a better understanding of the US Constitution than the US Supreme Court at this time,” Williams told Reuters on Wednesday. “Even an elected, public official doesn’t check their rights at the door when they get elected.”

Davis was jailed for five days in September for refusing to comply with a judge's order to issue marriage licenses in line with the Supreme Court ruling.

Davis has said her beliefs as an Apostolic Christian prevent her from issuing marriage licenses to same-sex couples. Her church belongs to a Protestant movement known as Apostolic Pentecostalism.

To keep a low profile, Davis went to the Vatican embassy in a sports utility vehicle with her hair in a different style than her normal look, Staver told CBS.

While conservative Christians, including some Republican presidential candidates, have said Davis is standing up for religious freedom, the American Civil Liberties Union has argued she has a responsibility as an official to issue the licenses, regardless of her views.

The ACLU went to court to ensure same-sex couples can obtain marriage licenses in Rowan County. In papers filed on Sept. 21 it asked the judge hearing the case to require Davis to stop making alterations to the licenses, such as removing any reference to the county clerk's office.

Plaintiffs who have sued Davis in federal court indicated the pope's meeting has no legal effect.

"The pope is not an American citizen, and he is not a member of our government. He is entitled to meet with whoever he likes and have any opinion he wants to have," Joe Dunman, an attorney representing plaintiff couples suing Davis, said in a statement.