The UK will "probably" begin formal negotiations to leave the European Union early in 2017, Foreign Secretary Boris Johnson has told the BBC.
The foreign secretary said it was still "subject for discussion" but the "Article 50 letter" would be produced "probably in the early part" of 2017.
But Number 10 said the government's position had not changed and Article 50 would not be triggered in 2016.
PM Theresa May has not yet given a clear statement on when it will begin.
Asked about Mr Johnson's comments, a spokeswoman for the prime minister said the government position on when it would trigger Article 50 was "not before the end of this year".
"The decision is hers [Mrs May's] and she will do that at a time which is most likely to get the best deal for Britain," the spokeswoman added.
'In their interests'
Speaking in New York to the BBC and Sky News on Thursday, Mr Johnson appeared to go further when he suggested the Article 50 process could begin early in 2017.
He told the BBC: "The government is working towards an Article 50 letter which as you know will be produced, probably, in the early part of next year.
"That's still subject for discussion but what is clear I think to our friends and partners in the EU is two broad principles: we are not leaving Europe;
"Although we are leaving the EU treaties, we do want to have the closest possible trading relationship and it's very much in their interests to achieve that... it's very much in their interests to do a great free trade deal with us, and I think that will happen."
He also told Sky: "We are talking to our European friends and partners in the expectation that by the early part of next year you will see an Article 50 letter. We will invoke that.
"In that letter I am sure we will be setting out some parameters for how we propose to take this forward. I don't think we will actually necessarily need to spend a full two years but let's see how we go."
Formal negotiations over the UK's withdrawal from the European Union cannot begin until the UK triggers Article 50 of the Lisbon Treaty.
Mrs May earlier welcomed European Parliament President Martin Schulz to Downing Street, on a two-day visit to Britain.
In a statement ahead of the visit, Mr Schulz said: "The future deal between the EU and the UK must be good for all sides and must be one which allows the UK and the EU to keep working closely together on various aspects."
He added: "In London I will also stress why the European Parliament favours the earliest possible triggering of Article 50, which is a pre-condition to opening negotiations."
On arrival at Downing Street, Mr Schulz admitted the European Parliament was "not the easiest" partner to work with - with 750 members from 28 countries representing 300 parties - but said he was in Britain "to listen and to learn".
Mrs May said she was looking forward to working with the European Parliament and acknowledged the "understanding" shown by European partners that the Article 50 process would not be triggered before the end of 2016.
"I think this period of preparation is valuable for all concerned and while we are going to leave the European Union, we are not leaving Europe," she said.
Mr Schulz, a member of Germany's centre-left Social Democrats, will also meet Mayor of London Sadiq Khan and Labour leader Jeremy Corbyn on his visit.