The United Kingdom will pay France 480 million pounds ($A876 million) over three years to try to stop migrants from travelling in small boats across the Channel, helping to fund enhanced patrols, the use of drones and a detention centre.

At a summit designed to rebuild ties after years of bickering over Brexit, French President Emmanuel Macron greeted UK Prime Minister Rishi Sunak with smiles and mutual back-slapping before they agreed to work more closely together.

Macron told a joint news conference that relations had been strained by the UK's departure from the European Union while Sunak said the time had come for a new relationship, an "entente renewed".

"If we are honest the relationship between our two countries has had its challenges in recent years," Sunak said at a press conference alongside Macron.

"Today we have taken co-operation to an unprecedented level."

In office since October, Sunak has made stopping small boats a priority after the number of migrants arriving on the south coast of England soared to more than 45,000 last year, up 500 per cent in the last two years.

He has proposed new legislation to bar those arriving in small boats from claiming asylum but for this he needs the co-operation of French authorities to intercept the boats and break the people trafficking rings behind the flow of arrivals from Afghanistan, Iran, Syria and others.

As part of the new deal, the UK will help fund a detention centre in France while France will deploy more personnel and enhanced technology to patrol its beaches.

Officers from both countries will also look to work with countries along the routes favoured by people traffickers.

The funding package will be paid in instalments, with the UK paying 125 million pounds in 2023-24.

The UK said France would contribute significantly more.

"We will develop operational needs and will reinforce co-ordination," Macron said while adding that to go further and address the issue of whether migrants could be returned to France would require agreement across the whole bloc.

While the number of applications for asylum in the UK hit a 20-year high of nearly 75,000 in 2022, it is still below the EU average.

And many EU members are themselves at odds over how to handle migrants, and whether they should be returned to the first EU country they arrived in.

The meeting was the first summit of Europe's two biggest military and nuclear powers - both permanent members of the United Nations Security Council - in five years.

Sunak and Macron struck up a personal rapport at the COP27 summit in Egypt in November during their first face-to-face meeting, two weeks after Sunak became prime minister, with their warm relationship labelled "Le Bromance" in UK newspapers.

The two former investment bankers, accompanied by seven ministers on each side in Paris, met business leaders from both countries to deepen their economic relationship.

While it will take time to determine whether the agreement can reduce the number of people making the perilous journey across the channel, Sunak is likely to tout the deal as another achievement after he agreed new terms with the EU on Northern Ireland.

Later this month, King Charles will also travel to France on his first state visit as monarch.