Guterres told reporters in the talks venue, Crans-Montana, Switzerland that despite "very strong" commitment on all sides the conference had closed "without an agreement being reached."

Sources cited by Reuters said Thursday night's session had been marred by yelling and Guterres called a halt at 2 a.m. early Friday, prior to heading to Hamburg for the G20 summit.

Read more: Cyprus peace process stalls over school history dispute

Guterres, who appeared downcast at his press conference, did not elaborate on the cause, but added that the halt did not mean "other initiatives cannot be developed in order to address the Cyprus problem."

A happier moment in January; Greek Cypriot President Nicos Anastasiades (R) and Turkish Cypriot leader Mustafa Akinci with Guterres (C)

Guterres had flown in on Thursday to press Greek Cypriot President Nicos Anastasiades and Turkish Cypriot leader Mustafa Akinci to seal a deal reuniting the east Mediterranean island.

Cyprus has been divided since a 1974 Turkish invasion triggered by a coup by Greek Cypriots seeking union with Greece.

Turkey, which still has about 30,000 troops in northern Cyprus, had been insisting at the talks that its forces remain.

'Difficult exercise'

On Thursday, Greek Foreign Minister Nikos Kotzias asserted that the Greek side had done all it could to rescue the talks. "It was a very difficult exercise," he said.

The White House said US Vice President Mike Pence had rung rival Cypriot leaders to underscore US support for a settlement.

Greece, Britain and Turkey are guarantor powers of Cyprus in a 1960 independence treaty.

ipj/bw (Reuters, AFP, AP)