A dispute between the U.K. and France over fishing rights simmers as the G20 summit approaches.

As world leaders prepare to meet for this weekend’s Group of 20 summit in Rome on some of the greatest challenges facing the global community, a dispute much closer to home for Britain and France is swirling in the background.

A growing disagreement between the two countries over post-Brexit fishing rights in the English Channel has become a focal point for the summit and is expected to be a topic of discussion for the nations’ leaders.

George Eustice, Britain’s environment secretary, told Sky News on Friday that Prime Minister Boris Johnson was likely to raise the dispute with President Emmanuel Macron of France during the meetings.

Tensions have flared in recent weeks over fishing licenses. On Wednesday, France detained a British boat near the port of Le Havre and fined another two. The French authorities have threatened further action beginning on Tuesday unless Britain issues licenses to dozens of French boats.

France has said that a failure to issue the licenses would renege on a post-Brexit fishing agreement. Clement Beaune, France’s minister for Europe, said in a statement that unless the licenses are issued, the country will consider other retaliatory measures and has not ruled out limiting the electricity supply to the Channel Islands, British dependencies off the coast of France.

London has said that the French actions could violate international law. Liz Truss, Britain’s foreign minister, said in a statement that the government had summoned the French ambassador for talks on Friday “to explain the disappointing and disproportionate threats made against the U.K. and Channel Islands.”

The dispute has become increasingly heated as the two nations try to navigate a new relationship after Britain’s exit from the European Union. The fishing dispute even resulted in a short naval standoff in May after a longstanding agreement in the shared waterway ended and a post-Brexit agreement was forged in December.

Under that new agreement, European fishers can continue to work in some British waters if they prove that they had worked in the area before Brexit, but France and Britain have locked horns over what documentation is required. Last month, Britain and the Channel Islands refused licenses to about 240 boats that the French authorities say have fishing rights under the agreement.

France has threatened to add extra measures including checks and controls on other goods entering Britain from French ports, raising fears of further disruption to Britain’s already struggling transportation industry.