The EU’s patience is running thin and it could use all the tools at its disposal if the U.K. fails to put a stop to unilateral actions and threats, said the official who asked not to be named discussing confidential matters. The official declined to detail which tools could be used, saying that earlier infringement and arbitration procedures were not working.

The dispute is escalating at a sensitive time for British prime minister Boris Johnson, who hosts world leaders in the U.K. for the Group of Seven summit later this week. The Brexit arguments encroached on a phone call Johnson held with French President Emmanuel Macron ahead of the gathering, on Monday.

Johnson “stressed” to Macron that “both the U.K. and the EU have a responsibility to find solutions” to the dispute over trade rules affecting Northern Ireland, a spokesman for the British premier’s office said. Johnson and Macron agreed to work together to avoid a repeat of tensions flaring over fishing rights, the spokesman added.

The EU voiced its frustration at the British approach ahead of talks between the two sides taking place Wednesday, which will seek solutions to prevent further unrest in Northern Ireland. The U.K. earlier urged the EU to show a “common-sense” approach to their post-Brexit future, and said it is working closely with the bloc.

Under the Brexit trade deal agreed in December, both sides have the right to impose retaliatory tariffs in extreme circumstances. Separately, the EU could prevent the U.K. financial services industry getting access to the single market.

Northern Ireland has been a major flashpoint between the U.K. and EU since Britain quit the bloc at the start of this year, sparking violent protests in opposition to new border checks and customs paperwork on trade crossing the Irish Sea. Meanwhile the EU has tabled legal action against the U.K. for unilaterally changing the terms of their post-Brexit deal with respect to Northern Ireland, which has a border with the Republic of Ireland, a member of the EU.

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The onus is on the U.K. to fulfill its obligations on the Brexit agreement’s Northern Ireland Protocol or face a much more confrontational future, said the official, who said EU experts still did not have access to the most basic IT systems to determine what goods are moving where, and thus assess risks linked to plant and animal health.

The EU is open to finding solutions but there are limits to what can be achieved given the political decisions the U.K. has made, the official said, citing Brexit itself and the form of Brexit the U.K. has chosen. Solutions can only be found within the framework of the protocol, the official added.