Britain's Brexit minister warned Friday that time was "running out" on talks with the European Union as London threatened to suspend a deal over Northern Ireland.
Britain and the EU are trying to thrash out solutions to problems caused by the trading arrangements in Northern Ireland agreed as part of the UK's acrimonious departure from the bloc.
"We hope to make some progress. But honestly, the gap between us is still quite significant. But let's see where we can get to," David Frost told journalists as he arrived for the latest round of negotiations in Brussels.
"Time is running out on these talks. If we're to make progress, we need to make progress soon."
The differences over Northern Ireland have embittered relations between Brussels and London and threaten to cause a trade war that could bring bilateral trade to a standstill.
Looming over the talks is Article 16 of the protocol -- which gives either side the right to suspend parts of the trading arrangement in exceptional circumstances.
"We're not going to trigger Article 16 today, but Article 16 is very much on the table," Frost said.
Britain has threatened to use the provision by early November if the EU does not redraw the protocol. Europe could retaliate a month later once it has done so.
Frost insisted that the European Commission, the EU's executive arm, has to "listen" to demands to rewrite the protocol laid out by London if it wants to avert a breakdown.
The British government is pushing for major changes such as ending the oversight role of the European Court of Justice.
But Brussels refuses to renegotiate the protocol and has instead offered to ease customs checks on British goods entering Northern Ireland.
A European diplomat said the Commission was increasingly readying itself for the possibility London could trigger Article 16 and warned of a "strong reaction" from the EU if that happened.
The diplomat said that might involve Brussels suspending the overall post-Brexit trade deal -- a move that could plunge ties between the two sides and put them back to square one.
The dispute over Northern Ireland comes as Britain and France are locked in another furious post-Brexit dispute over fishing rights.
The row has added to a litany of problems between the Channel neighbours in the wake of Brexit that has plunged relations to a level of rancour rarely seen in recent years.
