President Tayyip Erdogan will discuss tensions between Ukraine and Russia with his counterpart Volodymyr Zelenskiy in Kyiv on Thursday, after pitching Turkey as a mediator, and an official said he was not picking any sides in the crisis.

Erdogan's visit to Turkey's fellow Black Sea nation comes after visits to Kyiv by leaders of NATO members Britain, Poland, and the Netherlands amid the standoff. Turkey has good ties with Kyiv and Moscow but has said it would do what is necessary as a NATO member if Russia invades.

Russia has denied plans to invade Ukraine amid concern by many Western nations over its build up of more than 100,000 troops near the border, but has demanded sweeping security guarantees from the West and says it could take unspecified military measures if its demands are not met.

Ankara has previously offered to help defuse the standoff and Turkish diplomatic sources have said both Russia and Ukraine were open to the idea. Turkey has opposed the sanctions threatened by other NATO members in response to a military incursion by Russia.

Speaking to reporters before leaving for Ukraine, Erdogan said Turkey was calling on both sides to seek dialogue, adding the crisis must be resolved peacefully on the basis of international law.

"Today, we will have our meeting with Mr Zelenskiy. After a visit to China, (Russian President Vladimir) Putin has told us he would travel to Turkey," he said. "Without holding these two visits, these talks, it would not be right to think about what we can do."

"God willing we will successfully overcome this problematic period between these two countries," Erdogan said, adding that statements from both Ukraine and Russia had so far played down the prospect of a direct military conflict.

The talks were due to be start with a bilateral meeting between the presidents at 1000 GMT.

Drones

A Turkish official, speaking on condition of anonymity, told Reuters that Ankara expects tensions to ease after the talks and that Erdogan will deliver messages that include calling on both sides to exercise restraint.

Turkey's "approach is not picking one side or standing against one country in the tensions," the official said, adding that Ankara wanted continued cooperation with both countries.

Turkey shares the Black Sea with Ukraine and Russia. Erdogan has said conflict would be unacceptable in the region and warned Russia that an invasion would be unwise.

While forging cooperation on defence and energy, Turkey has opposed Moscow's policies in Syria and Libya, as well as its annexation of the Crimean peninsula in 2014. It has also sold sophisticated drones to Ukraine, angering Russia.

Ukrainian Defence Minister Oleksii Reznikov told a briefing ahead of Erdogan's visit that Turkey and Ukraine will press ahead with a plan to build drones in Ukraine. The two countries will also sign a free trade agreement, along with several more deals.