French President Emmanuel Macron has said Britain and France must reduce risks posed by relying too much on the United States and China for trade.
In an address to the British parliament he said: "We will have .... to de-risk our two countries for the excessive dependencies on both the US and China.
"We want an open world. We want to co-operate, but not to depend," Mr Macron said.
On Brexit, he said that Britain's 2020 departure from the European Union was "deeply regrettable" but the result of its 2016 referendum was respected.
It was "a decision that we respect even if we found it deeply regrettable", he told politicians as he became the first EU head of state to make a formal visit to Britain since Brexit.
He said a UK-France Summit at Downing Street this week will mark a "new stage" to scale up co-operation between the two countries.
"Our two countries, the only European nuclear weapon states, the leading armed forces of the continent, together accounting for 40% of European military budgets, both fully shoulder the responsibility when it comes to European security."
He said both countries are faced with new threats, "with aggressive nuclear powers, with sometimes hesitating alliances, and the return of major conflict on our continent".
Mr Macron said there is an expectation that the UK and France, "faced with revisionist neighbours" have a "special responsibility for the security of the continent" and it is time to "make sure that not only our two countries will save themselves by their own exertions, but also that we will save Europe by our example and our solidarity".
He said Europe will never abandon Ukraine, adding that Britain and France will work with the 'coalition of the willing' until the last minute to secure a ceasefire.
"We will fight till the very last minute in order to get the ceasefire, in order to start the negotiations to build this robust and sustainable peace, because this is our security and our principles together which are at stake in Ukraine.
"This coalition was just a signal that Europeans will never abandon Ukraine - never," he added.
Relations between the UK and France had soured during Brexit but British Prime Minister Keir Starmer has sought to improve the UK-France relationship since coming to power just over a year ago.
Both countries have led European efforts to provide security guarantees for Ukraine, should a peace deal be brokered. The effort has been described by the British side as a "coalition of the willing".
A meeting of the coalition is due to take place later this week, while Mr Macron is in London.
Mr Starmer has also stressed the importance of working closely with France as his government tries to reduce illegal boat crossings.
It is hoped progress on this issue can be made during the state visit, with both countries understood to be discussing a "one in, one out" policy which would see deportation of illegal immigrants to France in return for people who have the right to be in the UK.
Home Secretary Yvette Cooper has said that France will be introducing new tactics to stop boats that are already in the water.
Aditional reporting Tommy Meskill
