The U.K. and the European Union agreed to intensify post-Brexit negotiations over Northern Ireland, as Foreign Secretary Liz Truss led the British side for the first time in a meeting at her official country residence.

Truss, who succeeded former Brexit chief David Frost in December, and European Commission Vice President Maros Sefcovic held talks at Chevening House on Thursday and Friday, ending with a plan to meet again on Jan. 24.

“We share a desire for a positive relationship between the EU and the U.K. underpinned by our shared belief in freedom and democracy,” Sefcovic and Truss said in a joint statement that called their meetings “cordial.”

The tone marked a positive shift after the more confrontational meetings last year when the U.K. side was led by David Frost.

Negotiations have been at a virtual standstill for months with Truss warning on Jan. 9 that she is prepared to unilaterally override parts of the post-Brexit agreement on Northern Ireland if talks fail. Sefcovic said recently that the foundation of the entire deal between the U.K. and EU would be jeopardized if London did that.

Britain’s main complaint is that the protocol, which places an effective customs border down the Irish Sea to ensure no hard border on the the island of Ireland, disrupts trade between Northern Ireland and the rest of the U.K. The protocol was signed and agreed by the British government in 2019.

The U.S. is monitoring the talks and urging both sides to come up with a solution, U.S. Trade Representative Katherine Tai said on Wednesday. President Joe Biden has consistently underlined the importance of not allowing Brexit to put at risk the Good Friday Agreement of 1998, which ended the conflict in Northern Ireland.

Truss’s own political ambitions overshadow the negotiations as she has positioned herself as a potential successor to Prime Minister Boris Johnson. Options include picking a fight with the EU that would curry favor with her Conservative Party faithful or cutting a deal to avert a trade war.

The EU has indicated it would slap tariffs on British goods in response and the move would be strongly condemned by the U.S., with which Britain is trying to secure a trade deal.

Another U.K. complaint is that the European Court of Justice has oversight of the protocol, and the British government doesn’t want it to be the final arbiter of disputes. The ECJ’s role is due to Northern Ireland remaining in the EU’s single market for goods, and the ECJ enforces single market rules.

The EU has proposed concessions around the customs burden faced by traders moving goods across the Irish Sea, but has been unwilling to discuss changes to the ECJ role in the protocol. So far, the U.K. has said the EU’s proposals don’t go far enough to address their concerns.