LONDON — Ireland’s prime minister says it is “only a matter of time” before same-sex marriage is legalized in Northern Ireland — the only part of the United Kingdom where it still is banned.

Prime Minister Leo Varadkar, Ireland’s first openly gay leader, made the comments at a gay pride event on Saturday in Belfast.

Northern Ireland remains the only part of the British Isles where same-sex marriages are not allowed. A 2015 voter referendum legalized them in the republic of Ireland.

The issue has been one of the sticking points preventing the restoration of the Catholic-Protestant power-sharing government in Northern Ireland.

The Democratic Unionists, Northern Ireland’s biggest British Protestant party and a key partner to British Prime Minister Theresa May’s government, has opposed same-sex marriage.

The Catholic nationalist Sinn Fein supports it.