NEWPORT, Wales, Britain, Sept. 4 (Xinhua) -- NATO will be working even closer together with Ukraine to help the latter reform its defense sector and build a strong modern army, NATO Secretary General Anders Fogh Rasmussen said Thursday.

Ukrainian President Petro Poroshenko also attended the meeting held by the NATO-Ukraine Commission (NUC).

"Ukraine has been an active and reliable partner to NATO over many years. We highly value our partnership," Rasmussen said in his opening remarks ahead of the meeting at the on-going NATO summit in Newport, southeast Wales of Britain.

"We stand united in our support of Ukraine sovereignty and territorial integrity, and we uphold the rights of every country to choose its future, free from outside interference," he added.

He added that an independent, sovereign and stable Ukraine "firmly committed to democracy and the rule of law" is key to Euro-Atlantic security.

Greeting Poroshenko in the opening remarks, the NATO chief suggested that now is "a testing time" for Ukraine.