The U.K. warned the European Union not to start a trade war if Boris Johnson’s government suspends part of the Brexit settlement over Northern Ireland, saying a strong retaliation would exacerbate problems.

“I hope everyone can step back from that,” U.K. Brexit Minister David Frost told BBC Radio on Wednesday. “I don’t see why it would help for the response to that from the European Union to be sanctions, retaliation and making trade more difficult.”

Both sides are again locked in talks to resolve the thorny question of how Northern Ireland fits into post-Brexit rules on commerce, with Frost calling for a fundamental overhaul of the U.K.’s divorce deal with the EU because it’s caused a decline in trade between the region and mainland Britain. The bloc has proposed concessions including reducing the burden of customs checks, but Frost has said they don’t go far enough.

If the U.K. isn’t happy with the outcome of the negotiations it has said it will activate Article 16 of the Northern Ireland protocol, which allows either side to suspend parts of the deal to address issues such as diversion of trade. One potential EU reaction to such a move would be to terminate the wider trade agreement with the U.K.

“I don’t understand why that would help the situation here,” Frost said. “Article 16 is a legitimate option within the treaty.”