Video report by ITV News Europe Editor James Mates.
Francois Hollande today warned Theresa May that she cannot pick and choose among EU rules as the two met to begin talking over a Brexit.
The French president has been among the toughest of negotiators over Britain's planned EU exit.
Today his language was more conciliatory - but he stressed that the UK can't enjoy unfettered access to the single market unless it also allows free movement of EU nationals.
In turn, Ms May insisted that the UK will not be rushed into starting formal talks leading to a Brexit as she said it would take time to reach the right agreement.
Theresa May has insisted that she won't be rushed into triggering the start of a Brexit as she met Francois Hollande.
Mrs May said that "it will take time" to prepare for the start of formal steps towards the UK exiting the EU as she appeared at a press conference with the French president.
It comes after Mr Hollande said today he would urge Mrs May not to "drag on" the process.
Mrs May today said she had "excellent" and "very open" discussions over the issue - but there was more work to do.
As the UK leaves the EU we will have to determine how to maintain the closest possible economic relationship between our countries.
And it will take time to prepare for those negotiations.
I understand the need for certainty and confidence in the markets, and that is why I've already been clear that the UK will not invoke article 50 until before the end of this year.
Theresa May has arrived in Paris on her first foreign trip as the British prime minister.
She was met by the French premier Francois Hollande this afternoon as she arrived from Germany on a whistle-stop European tour.
Ms May is discussing the terms for a UK exit from the EU with fellow leaders.
Mr Hollande has already made clear that he will warn Mrs May not to drag her feet over the start of formal talks over a Brexit.
Francois Hollande will tell Theresa May that Brexit talks must start quickly when the pair meet today.
The French president is expected to say he does not want there to be any "pre-negotiations".
Mr Hollande and the prime minister will hold talks on Britain's plans to quit the EU when they meet in Paris.
The French President will host a working dinner at the Elysee Palace, a day after Mrs May met German counterpart Angela Merkel.
At discussions in Berlin, the Chancellor said Britain should "take a moment" over its plans to sever its ties with Brussels but warned against leaving the negotiations "up in the air".
Theresa May and Francois Hollande will discuss Britain's plans to quit the European Union when they meet for talks on Thursday in Paris.Read the full story ›
Video report by ITV News deputy political editor Chris Ship.
Theresa May warned that the UK would not be rushed into leaving the EU as she met Angela Merkel today.
The new British prime minister needs to win over the German chancellor, who holds more power than anyone else in Europe over any deal which is finally agreed.
In Berlin, some expressed concern over the apparent lack of a plan for a Brexit after the UK voted to leave.
May's handling off the issue is likely to be among the key moments of her time in office - and that work started in earnest today.
What birthday present can you get the world leader who has everything?
Theresa May settled on a pair of books reflecting a shared love of walking as she marked Angela Merkel's 62nd birthday during a visit to Berlin.
Ms May handed her counterpart - who turned 62 on Sunday - a new edition of Coast To Coast With Wainwright, a classic photographic book from 1973 on beauty spots between the Irish and North seas.
She also presented a copy of Great Mountain Days In Snowdonia, which includes a guide to walks in the National Park.
The prime minister included a handwritten message of birthday wishes with the presents, which she picked out herself.
Theresa May said that Britons sent a "very clear" message pushing for the country to take back control of its borders when they voted for Brexit.
Her comments at a meeting with the German chancellor Angela Merkel are likely to add to tension over the terms of the UK's exit from the EU.
Ms May must square her commitment to curb immigration with the economic need for free access to the bloc's markets.
Europe has made it clear that Britain cannot have free trade without free movement - and that is likely to prove a sticking point in any talks.
Theresa May has insisted that Brexit will not mean "walking away from our European friends" as she embarked on her first foreign trip since being made prime minister.
Ms May, appearing alongside German chancellor Angela Merkel in Berlin, insisted that the UK would remain an "outward-looking country" after the European Union referendum result.
I have been clear that Brexit means Brexit and the United Kingdom is going to make a success of it.
But I also want to be clear here today, and across Europe in the weeks ahead, that we are not walking away from our European friends.
Britain will remain an outward-looking country and Germany will remain a vital partner and a special friend for us.
Theresa may have brushed up on her German skills for her first foreign trip since being made prime minister a week ago.
She greeted the German chancellor Angela Merkel in her own language as they hosted a joint press conference today.
"I am delighted to be in Berlin" she said in German, hastily adding: "I will now go into English".
Her efforts seems to have made a good early impression on Ms Merkel as the pair got to know each other at their first meeting.
The chancellor appeared visibly surprised and pleased at the gesture.