Ukrainian and Slovak prime ministers Denys Shmyhal and Robert Fico began their meeting near the western Ukrainian border city of Uzhhorod on Oct. 7.
The two heads of government will discuss cooperation in energy security and infrastructure projects.
The meeting comes shortly after Fico's comments that as long as he is the prime minister, he will block Kyiv's entry into NATO.
"This is something that I have openly told Prime Minister Shmyhal, the Americans, and everyone else. As long as I am head of the Slovak government, I will direct the lawmakers under my control as chairman of the (ruling Smer) party never to agree to Ukraine joining NATO," Fico told Slovak media.
Ukraine applied for membership in September 2022 in the wake of Russia's full-scale invasion but has yet to receive an invitation. The step would require a unanimous agreement of all the 32 members.
"It would only create a basis for World War III. Because ... once Ukraine is a NATO member and a conflict similar to the current one breaks out, it will count as an attack on a NATO member, and some extremely dangerous mechanisms can be triggered," Fico said, reiterating his previously voiced positions.
Since returning to office in October 2023 after winning the Slovak parliamentary elections on a populist platform, Fico has sharply criticized military aid to Ukraine and sanctions against Russia. This represented a sharp shift away from the previous government's policy, which supplied Kyiv with extensive arms supplies, including Soviet-made MiG-29 fighter jets.
In turn, the Slovak prime minister spoke in support of Ukraine's EU membership and largely avoided breaking Western consensus in major decisions on support for Ukraine.
Last week, Fico also said he would visit Moscow next year for the 80th anniversary celebrations of the end of World War II. While the Slovak prime minister claimed the visit would not be connected to Russia's war, the Kremlin uses the annual victory celebrations for propaganda purposes and to showcase its military might.
"Next year will be the 80th anniversary of the end of World War II. Who will stop me from going to a peace rally in Moscow?” he asked.
"Why shouldn't I go? What does it have to do with the present?"
Fico previously met Shmyhal in Uzhhorod in January, during which both leaders signed a joint statement on bilateral relations.