Theresa May is making her first overseas visit as Prime Minister to meet German chancellor Angela Merkel in Berlin, ahead of a trip to Paris on Thursday for talks with French president Francois Hollande.
Mrs May will depart for Germany after facing MPs for her first session of Prime Minister's Questions in the House of Commons, where she is likely to be challenged over her insistence that she will not rush into immediately triggering the process of leaving the European Union.
Speaking before her departure for Berlin, the PM said she aimed to deliver a clear message to Mrs Merkel and Mr Hollande that Britain wants to maintain - and even strengthen - its close relations with their countries even after it has quit the EU.
She will make clear that she does not intend to start the two-year process of negotiating the terms of Britain's withdrawal under Article 50 of the Lisbon Treaty until the UK Government has had time to consult with the devolved administrations in Scotland, Wales and Northern Ireland, as well as different sectors of industry, about what its objectives in the talks should be.
Mrs May said: "I am determined that Britain will make a success of leaving the European Union and that's why I have decided to visit Berlin and Paris so soon after taking office.
"These visits will be an opportunity to forge a strong working relationship that we can build upon and which I hope to develop with more leaders across the European Union in the weeks and months ahead.
"I do not under-estimate the challenge of negotiating our exit from the European Union and I firmly believe that being able to talk frankly and openly about the issues we face will be an important part of a successful negotiation.
"I also want to deliver a very clear message about the importance we attach to our bilateral relationship with our European partners, not just now but also when we have left the European Union.
"These relationships have been vital in the past and they will be vital in the future as we continue to work together to keep our people safe and to support economic growth that benefits people across our countries."
Mrs May will hold her first face-to-face talks with Mrs Merkel over dinner in Berlin, and will also have a working dinner with Mr Hollande at the Elysee Palace on Thursday. Both visits result from invitations issued shortly after her elevation to the premiership last week.
In a sign of determination to ensure that the UK's relations with EU states will not be exclusively dominated by Brexit, Downing Street said it expected talks to focus on economic and trading relationships as well as co-operation on global challenges such as the migration crisis and the threat from Islamist terrorism.
Brussels has said that no formal or informal talks on Britain's future relations with the EU should commence until the UK has formally stated its intention to leave by invoking Article 50.
However, Downing Street sources said they did not expect national leaders to feel constrained from discussing the political realities created by the June 23 vote for Brexit.
Government lawyers told a court in London on Tuesday that Mrs May had made clear she did not intend to deploy the Article before the end of 2016, though Number 10 stressed that this was a decision for the Government to make.
The visits come after Mrs May travelled to Scotland and Wales in the first few days of her premiership. Number 10 says she is planning a trip to Northern Ireland soon.
On Tuesday, she met US Secretary of State John Kerry, who said during a visit to London that he expected her to pursue a "calm, thoughtful, reasonable" way to deal with Brexit.