NATO says it is "disappointed" by the sentence handed down to Ukraine's former Prime Minister Yulia Tymoshenko for abuse of office over a gas deal with Russia.

NATO spokeswoman Oana Lungescu said on Thursday the alliance hoped the sentence could be reversed "on the basis of the rule of law."

Tymoshenko, who once symbolised Western hopes for a democratic Ukraine, was sentenced on Tuesday to seven years in prison. She has launched an appeal against the sentence.

The verdict was condemned by the US and the European Union as politically motivated.

Ukraine abandoned its drive to join NATO after Viktor Yanukovych was elected president last year. But Ukraine remains a member of NATO's Partnership for Peace program for non-members and has sent troops to serve in NATO-led missions.