Donald Trump will allow gay couples to benefit from the same tax breaks for childcare as heterosexual couples.

The policy proposal was announced on Tuesday and will pay for childcare expenses through tax deductions and guarantee mothers six weeks of paid maternity leave. The benefits would be equally available to couples in same-sex marriages, putting it on the same footing as heterosexual marriages.

The move could damage his reputation with conservative evangelical groups who have been gradually warming to the Republican candidate.

The plan to pay for childcare was backed by his daughter Ivanka in an op-ed for The Wall Street Journal on Tuesday evening. But the article made no mention of the equal treatment of gay couples. She wrote: "[My] father is prepared to chart a new course that promotes strong families and celebrates their individual needs."

Trump also skipped over it during a 20-minute speech in Philadelphia to introduce the policy.

It was only in a policy paper handed out to reporters before the speech that Trump's campaign acknowledged: "The benefits would be available in the same way that the IRS currently recognizes same-sex couples: if the marriage is recognized under state law, then it is recognized under federal law."

Trump appeared to further dampen down his inclusion of same-sex couples later on Tuesday when he gave a speech in Iowa where more than half of registered Republican voters identify as evangelicals.

The plan was seen as a bid to soften Trump's image as he faces a deficit with college-educated women in the polls. He called for childcare to become tax deductible and said the policy would provide six weeks of maternity leave "to any mother with a newborn child whose employer does not provide the benefit" by tackling fraud in unemployment insurance.