The pope is not as liberal as many Americans seem to think, the conservative Catholic bishop of Philadelphia has said.

Those hoping Pope Francis will liberalise some of the Catholic's church teaching "risk being very disappointed," said Archbishop Charles Chaput, who will be the pope's host when he arrives in Philadelphia on Saturday.

"His vocabulary and emphases are different, like his personal style of leadership," he said.

"But that doesn't mean a change in content. People risk being very disappointed if they imagine it does."

A recent poll found that 66 per cent of Americans have a good opinion of the pope but Chabut has suggested that's because they have misinterpreted his message.

Pope Francis is known for his attempts to make the Church more inclusive and welcoming. When asked about gay clergy members he famously replied, "If a person is gay and seeks God and has good will, who am I to judge?"

On top of that Pope Francis said that women who have abortions could be forgiven if they repent.

However Chabut is right in saying that the pope has not actually shown much sign of liberalising Catholic teaching. The Vatican quickly clarified that the Church does not condone abortion after the pope's announcement. Francis has also said the ordination of women is a closed book and has recently reaffirmed the Church's teaching that homosexual acts are sinful, though homosexual orientation is not.

Chabut is the unofficial leader of conservative Catholicism in the US and has fiercely defended the Church's position on pro-life matters.

"The right to life is foundational," Chaput said. "Without it, all other rights are compromised."