WARSAW (Reuters) - The leaders of Germany and Turkey sought on Saturday to clear the air in their first private talks since the German parliament infuriated Ankara by branding the 1915 massacre of Armenians by Ottoman forces a genocide, but they did not overcome their differences.

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Chancellor Angela Merkel met Turkish President Tayyip Erdogan on the sidelines of a NATO summit in Warsaw to discuss the tensions in their often prickly but strategically important relationship.

Ties between Turkey and Germany - vital partners in efforts to curb mass migration to Europe - have been strained since the Bundestag passed the Armenian resolution on June 2. Ankara recalled its ambassador and threatened unspecified retaliation.

Turkey has since denied German parliamentarians access to the Incirlik airbase where 250 German soldiers are taking part in NATO operations against Islamic State militants in Iraq, causing anger in Berlin.

“We discussed all outstanding issues,” Merkel told reporters at a brief news conference. “The atmosphere was constructive ... and very businesslike in an effort to solve the existing conflicts.”

Asked whether the issues had been resolved, she said: “The differences don’t just disappear through such a discussion. But I believe it was important that we talked them through.”

A source close to the Turkish presidency said Erdogan had expressed his disappointment over the Bundestag resolution to Merkel, who said she would do her utmost to ensure this event would not harm German-Turkish relations.

“PUBLIC SHOWS AND MARKETING”

The source said Merkel also expressed satisfaction with the way Turkey was keeping its word in preventing refugees and migrants crossing the Aegean Sea to Greece after more than one million flooded into Europe last year, most ending up in Germany.

The Turkish source said Merkel had raised the issue of the Incirlik airbase and had asked Erdogan to restore access for lawmakers, who approve all military spending and investment in infrastructure at the base.

Erdogan replied that the airbase was not a place for “public shows and marketing” but Turkey would consider the request in the light of German statements on relations, the source said.

The two leaders also discussed intelligence cooperation in the fight against foreign fighters recruited by Islamic State in Syria, some of whom have returned to carry out attacks in Europe.