France's Europe minister on Wednesday warned Britain against abandoning an EU agreement on a post-Brexit trade with Northern Ireland.
European Affairs Minister Clement Beaune said the situation would create a "huge problem" and France was ready to respond.
"The UK is playing with the deal, not fully implementing it," Mr Beaune said on the sidelines of the Globsec Forum in Bratislava.
London and the EU agreed on a special protocol on trade with Northern Ireland as part of the Brexit deal, to prevent a hard border on the Irish island.
The UK has asked the EU to extend a grace period for introducing some rules on trade between mainland Britain and the British province.
The protocol is deeply unpopular among the pro-British unionists and politicians from the Democratic Unionist Party are pressing UK Prime Minister Boris Johnson to scrap it.
"If the UK thinks about leaving the protocol, this is a huge concern, a huge problem that cannot be accepted," Mr Beaune said. "No protocol means no deal.
"If a party, whether the UK or the EU, does not respect the agreement we can take measures within the framework of the agreement.
"We are ready to do it. We are not happy to do it, we are ready to do it."