Kerry is set to meet Thursday with his Russian counterpart Sergei Lavrov as a long-awaited truce around an airport in rebel-held Donetsk in eastern Ukraine appeared under threat, just hours after it was agreed.
   
The US and Russian top diplomats, who most recently spoke in late November during talks in Vienna on Iran's nuclear programme, are set to "discuss a range of topics of mutual interest including issues related to the Middle East", according to a US official.
   
The 57-member OSCE, headed by Swiss President Didier Burkhalter, is in charge of monitoring a shaky overall ceasefire between the Ukrainian army and separatist rebels in eastern Ukraine reached in September.

Kerry's flight defied heavy fog over the northern Swiss city and landed shortly before 7pm.

He was whisked to the Basel Exhbition Centre where the OSCE will kick off the two-day ministerial meeting on Thursday.

While Ukraine is a focus of the ministerial meeting, the diplomats will debate 20 draft declarations on security issues and concerns.

A parallel "civil society" conference got under way on Wednesday in Basel. 

Kerry, who flew in from Brussels, where he took part in a meeting of the US-led coalition against the jihadist Islamic State group, later met acting OSCE chairman Burkhalter.

Kerry later flies to London for a conference on Afghanistan.