Ambassadors from Ukraine and the 28 NATO allies will hold a special meeting at Ukraine's request on Monday to discuss the new flare-up in fighting in the east of the country, NATO said.
Ukraine invoked a clause of a NATO-Ukraine agreement which allows for crisis talks whenever Ukraine perceives a direct threat to its territorial integrity, political independence, or security.
The last extraordinary meeting of ambassadors from NATO and Ukraine was in August, although there have been meetings at ministerial and head of government level since then.
Pro-Moscow separatists, backed by what NATO says are Russian troops, have launched an offensive in southeastern Ukraine, shattering a five-month-old ceasefire. Russia blames Kiev for the surge in fighting.
NATO Secretary-General Jens Stoltenberg was also due to hold talks with European Union foreign policy chief Federica Mogherini on Monday but a NATO official said the meeting was scheduled before the latest increase in violence in Ukraine.
NATO has made clear it has no plans to intervene militarily in Ukraine, which is not a NATO member, but it has stepped up cooperation with Kiev, including creating five trust funds to help Ukraine improve its security forces.