Brexit talks go down to the wire ahead of EU summit

* Headway made in 11th-hour talks

* But still not clear if a deal at hand

* Irish border still the main obstacle

* PM Johnson would also need parliament backing

By John Chalmers and Gabriela Baczynska

BRUSSELS Oct 16 (Reuters) - British and EU officials were to resume talks to clinch a Brexit deal on Wednesday just a few hours after late-night negotiations wound up, but it was far from clear they would reach an agreement before a leaders' summit on Thursday.

Officials involved in the complex divorce between the world's fifth-largest economy and its biggest trading bloc said differences over the terms of the split from the 27 other member states had narrowed significantly.

French Finance Minister Bruno Le Maire told Europe 1 radio on Wednesday that there was a "glimmer of hope" that a Brexit deal can be reached before Britain's scheduled departure on Oct. 31.

But if an agreement is not ready for the Brussels summit, British Prime Minister Boris Johnson will almost certainly have to postpone Britain's exit again - for what would be the third time since the country voted in a referendum in June 2016 to quit the EU.

"The clock is ticking," said an EU official with knowledge of Tuesday's negotiations, which went into the night and ended at 1:30 a.m., about 16 hours after they had begun.

A British government spokesman described the talks as "constructive" and said the negotiators had continued to make progress.

The main sticking point in talks has been the border between EU member Ireland and the British province of Northern Ireland.

The question is how to prevent the border becoming a backdoor into the EU's single market without erecting controls which could undermine the 1998 peace agreement that ended decades of conflict in the province.

Irish Prime Minister Leo Varadkar told reporters in Dublin on Tuesday that talks had moved in the right direction.

The EU official said "one of the major outstanding issues" was agreeing on Britain's application of common EU rules and standards designed to ensure fair competition.

A second EU official said late on Tuesday that an agreement was "close but not 100% certain". (editing by John Stonestreet)