European Council President Donald Tusk says Brexit discussions with Theresa May have got "off to a good start" after a meeting at Downing Street.
The meeting to discuss "the way ahead on Brexit" came less than a week after Mr Tusk announced the EU's draft guidelines for EU exit negotiations in response to Theresa May triggering Article 50.
Following the meeting Mr Tusk tweeted: "Meeting PM May to make sure Brexit talks get off to good start. Agreed to stay in regular contact throughout process."
An EU source told Sky News the talks had been "good and friendly".
The simmering tensions between Spain and the UK over Gibraltar are understood to have been discussed by the two, after the guidelines effectively gave Spain a veto over the British territory's future.
The source said there would be regular contact between Mrs May and Mr Tusk for a "constructive approach... when talks on some issues like Gibraltar inevitably will become difficult".
The EU stance on Gibraltar had triggered an angry response from some UK politicians.
Former Conservative leader Lord Howard told Sky's Sophy Ridge on Sunday programme that Theresa May would show the same resolve to defend Gibraltar as Margaret Thatcher did the Falklands.
Spanish foreign minister Alfonso Dastis responded by telling the UK to calm down and not to "lose tempers".
Mr Tusk disclosed he would be visiting Mrs May for talks ahead of the EU summit meeting at the end of the month when he unveiled the Brexit negotiation guidelines last week.
Also thought to have been discussed was the timing of trade talks.
The draft guidelines said the UK would have to make "sufficient progress" on key divorce issues such as settling the Brexit bill and guaranteeing the rights of EU citizens before starting talks on a future trade deal with the EU.
However, MEPs in the European Parliament on Wednesday voted to delay trade talks until the key issues on Brexit were "fully resolved" - setting the bar for the UK higher.
In an interview with Sky News this week, Mrs May conceded that the UK might not get a trade deal signed off in the two years she had previously suggested.
The Prime Minister had wanted to see trade discussions start at the same time as the talks over the Brexit agreement.
She also appeared to soften her stance on freedom of movement after Brexit, indicating curbs would not be imposed in the immediate aftermath of leaving the EU.
Labour accused her of breaking her Brexit promises.