(Reuters) - In a dramatic shift in tone, a Vatican document said on Monday that homosexuals had "gifts and qualities to offer" and asked if Catholicism could accept gays and recognize positive aspects of same-sex couples.

The document, prepared after a week of discussions at an assembly of 200 bishops on the family, said the Church should challenge itself to find "a fraternal space" for homosexuals without compromising Catholic doctrine on family and matrimony.

While the text did not signal any change in the Church's condemnation of homosexual acts or its opposition to gay marriage, it used language that was less judgmental and more compassionate than past Vatican statements under previous popes.

The document will be the basis for discussion for the second and final week of the assembly, known as a synod, which was called by Pope Francis and focuses on the theme of the family.

It will also serve for further reflection among Catholics around the world ahead of another, definitive synod next year.

"Homosexuals have gifts and qualities to offer the Christian community: are we capable of welcoming these people, guaranteeing to them a further space in our communities? Often they wish to encounter a Church that offers them a welcoming home," said the document, known by its Latin name "relatio".

"Are our communities capable of proving that, accepting and valuing their sexual orientation, without compromising Catholic doctrine on the family and matrimony?" it asked.

John Thavis, Vatican expert and author of the bestselling 2013 book "The Vatican Diaries", called the document "an earthquake" in the Church's attitude towards gays.

"The document clearly reflects Pope Francis' desire to adopt a more merciful pastoral approach on marriage and family issues," he said.

A number of participants at the closed-door synod have said the Church should tone down its condemnatory language when referring to gay couples and avoid phrases such as "intrinsically disordered" when speaking of homosexuals.

That was the phrase used by former Pope Benedict in a document written before his election, when he was still Cardinal Joseph Ratzinger and head of the Vatican's doctrinal department.

EDUCATIONAL CHALLENGE

The language and tone of Monday's document, read to the assembly in the presence of Pope Francis, appeared to show that the advocates of a more merciful tone toward homosexuals and Catholics in so-called "irregular situations" had prevailed.

It said that the 1.2 billion-member Church should see the development of its position on homosexuals as "an important educational challenge" for the global institution.

While the Church continued to affirm that gay unions "cannot be considered on the same footing as matrimony between man and woman", it should recognize that there could be positive aspects to relationships in same-sex couples.

"Without denying the moral problems connected to homosexual unions it has to be noted that there are cases in which mutual aid to the point of sacrifice constitutes a precious support in the life of the partners," the document said.

Pope Francis has said the Church must be more compassionate with homosexuals, saying last year: "If a person is gay and seeks God and has good will, who am I to judge."

The Church teaches that while homosexual tendencies are not sinful, homosexual acts are.

The document also showed considerable opening to heterosexual couples who were married only in civil services or who were living together, mentioning "positive aspects" of such unions, especially if the couple saw them as a prelude to marriage in the Church.

While Church marriages clearly were "the ideal" for Catholics, it said, there were "constructive elements in those situations that do not yet or no longer correspond to that ideal".

Catholics used to call such cohabitation arrangements "living in sin", another phrase that bishops at the synod were urged not to use when speaking about these couples.

(Additional reporting by Tom Heneghan; Editing by Crispian Balmer)