CHISINAU, Moldova (Reuters)-The presidents of Azerbaijan and Armenia held "constructive" talks on the Nagorno-Karabakh conflict on Thursday and will meet again soon, the US Co-chairman of the OSCE Minsk Group said.

Success in the talks in the Moldovan capital has been seen as a key to easing the way for a restoration of relations between Armenia and Turkey.

Minsk Group US Co-chairman Robert Bradtke said the meeting between Azeri President Ilham Aliyev and Armenia's Serzh Sargsyan continued "a positive dynamic in the discussions".

"The discussions were serious and constructive. They have agreed to meet again in the near future," he told reporters.

The Russian co-chair Yuri Merzlyakov said the next meeting between the two men would be "relatively soon".

Aliyev and Sargsyan were due to stay on in Chisinau on Friday when they will meet Russian President Dmitry Medvedev as part of a summit of Commonwealth of Independent States.

Analysts said the outcome of Thursday's talks in Chisinau was important in terms of a scheduled meeting in Zurich on Saturday when Armenia and Turkey are scheduled to sign the protocols to establish and develop relations.

Merzlyakov, answering a reporter's question, said the planned Zurich meeting between Armenia and Turkey did not crop up in the Chisinau talks.

French co-chair Bernard Fassier, speaking in Russian, said the Minsk process was independent and "without links to other processes."

Aliyev and Sargsyan posed, unsmiling, for cameras at the start of talks which were held at the residence of the U.S. ambassador.

A Turkish parliamentarian, speaking before Thursday's talks, said it would be difficult to secure parliamentary approval in Turkey for any normalization of ties with Armenia if the talks on Karabakh did not show progress.