Tension between Ukraine and neighboring Russia continue to mount as a meeting between the two and other members of a key European security expected.
Ukraine Foreign Minister Dmytro Kuleba said Russia had ignored formal requests to explain the build-up of troops.
He said the next step was requesting a meeting within the next 48 hours for transparency about Russia’s plans.
Russia has denied any plans to invade Ukraine despite the build-up of some 100,000 soldiers on Ukraine’s borders.
But with the US saying Moscow could begin with aerial bombardments “at any time” more than a dozen nations have urged their citizens to leave Ukraine.
British Armed Forces Minister James Heappey said the UK would support whatever Ukraine decided to do.
But Ukraine is taking moves to keep its airspace open after KLM became the first major airline to suspend flights to the capital Kyiv.
Ukraine said it was ready to assume financial obligations for flight safety in the country’s airspace.
Other airlines could follow KLM because of the rising insurance costs.
Ukraine’s deputy head of the office of the president, Kirill Tymoshenko, said at the weekend that the country was willing to underwrite some of the costs.