UK Prime Minister Theresa May promises to pay $62 million for fences, security cameras and other measures in the coastal town of Calais and British ports overlooking the English channel.
Britain and France on Thursday signed a new deal to boost border security after a request by French President Emmanuel Macron, concerned at the number of migrants in Calais trying to reach British shores.
The two sides agreed on the "signature of a new treaty to strengthen the management of our shared border," according to a joint statement following a summit between Macron and British Prime Minister Theresa May.
At a press conference with Macron following the summit, May said that Britain and France "remain committed to the principles of the long-standing Le Touquet agreement" which was signed in 2003.
But she said "additional measures" had now been agreed for Calais and other border points, as Britain pledged an additional $62 million (50 million euros, £44.5 million ) for border security in France.
The funding will go towards fencing, CCTV and detection technology, May said.
Macron called the agreement the "Sandhurst Treaty," and said it would improve management of the border as the two leaders held talks at the Sandhurst military academy, southwest of London.
"What the people in Calais are going through is not satisfactory and that is the reason why our interior ministers have signed today in our presence a new treaty," Macron said.
He says it will cut the time it takes to process migrants who gather in the northern French port of Calais hoping to reach Britain, and to treat them more humanely and efficiently.
Macron wants Britain to take more migrants from Calais but no figure was given Thursday.
Macron says the border issue "is a common challenge and we shall succeed together."