Theresa May has distanced herself from comments made by Boris Johnson suggesting formal talks on Brexit will begin by "the early part of next year".
The Foreign Secretary said ministers were working towards triggering Article 50 of the EU treaties - marking the official start of negotiations - in the first part of 2017.
Speaking in New York where he has been attending the United Nations, Mr Johnson also suggested the discussions could be wrapped up before the two-year deadline.
He told Sky News: "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."
Mr Johnson's remarks are likely to be welcomed by pro-Leave campaigners as an indication the Government is preparing for a "hard Brexit".
They go further than Prime Minister Theresa May, who has said only that Article 50 will not be invoked before the start of 2017.
But a Number 10 spokesman distanced the Government from Mr Johnson's comments soon after they were aired.
The spokesman said: "The Government's position has not changed - we will not trigger Article 50 before the end of 2016 and we are using this time to prepare for the negotiations."
It came as European Parliament president Martin Schulz visited Britain and held talks with Mrs May about Britain leaving the EU.
Mr Schulz is pressing for the UK and hurry up and get on with Brexit as he is keen for negotiations to finish before European elections in mid 2019, meaning Article 50 would have to be triggered by May next year.
Speaking at the beginning of the hour-long talks, Mrs May reiterated that formal negotiations would not be launched this year.
She said: "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.
"And we want the EU to continue to be strong and have a close relationship with it, and I think that will be in both our interests."
Mr Schulz admitted the European Parliament was "not the easiest" partner to work with, but said he hoped to forge close co-operation with the UK.
He said: "The European Parliament is involved in all activities before, and once you have triggered, Article 50, and I'm here to listen and to learn also about the state of preparation about your vision for the negotiation.
"But also to pass the message that we are, as the European Parliament, constructive but, logically, also not the easiest partner in the relationship, because the European Parliament is a very heterogeneous chamber with 750 members from 28 countries representing 300 parties."
Mr Schulz will meet Labour leader Jeremy Corbyn on Friday before delivering a speech at the London School of Economics about the UK's looming exit from the EU.