Brad Pitt has said this week the pledge he and Angelina Jolie took to hold off on marriage until equality was achieved for everyone in the US is proving hard to keep.

In an interview with the Hollywood Reporter, the 48-year-old actor said he did not know whether they would be able to go the distance on the promise.

He told the magazine: “We’d actually like to, and it seems to mean more and more to our kids. We made this declaration some time ago that we weren’t going to do it till everyone can. But I don’t think we’ll be able to hold out.

“It means so much to my kids, and they ask a lot. And it means something to me, too, to make that kind of commitment.”

Equal marriage legislation is being considered in Washington, New Jersey and Maryland. In Maine, enough signatures have been collected on a petition to trigger a public ballot.

But in Minnesota and North Carolina, discussions are taking place to introduce constitutional amendments defining marriage as being between a man and a woman, meaning Pitt and Jolie’s prerequisite of universal marriage equality is unlikely to happen soon.

In New Hampshire, legislators are preparing a vote on reintroducing the state’s gay marriage ban, which was overturned as of 1 January 2010.

Charlize Theron made a similar pledge in 2009 about then-boyfriend Stuart Townsend. Theron originally hails from South Africa, where gay marriage is legal.

Pitt would not say whether or not he had proposed to Jolie.

When New York introduced equal marriage laws last year, he said: “It is encouraging that New York has joined the movement to grant equal marriage rights to its citizens.

“But it is each American’s Constitutional right to marry the person they love, no matter what state they inhabit. No state should decide who can marry and who cannot.”

He added: “Thanks to the tireless work of so many, someday soon this discrimination will end and every American will be able to enjoy their equal right to marriage.”