Stoltenberg added that the bloc will help Ukraine to move towards membership of the alliance. He emphasized that there will be "severe costs" for Russia should it invade Ukraine.
He also said that this week's security negotiations with Russia may not resolve all issues at once but still could provide a pathway to avoid conflict, Sputnik reported.
"It is possible to make deals with Russia...What we are hoping for is that we can agree on a way forward, that we can agree on a series of meetings, that we can agree on a process," Stoltenberg said, quoted by Reuters.
Stoltenberg's statements come as delegations from Russia and the US have started talks on security guarantees in Geneva. Earlier, Russia's Deputy Foreign Minister Sergei Ryabkov said that although Moscow was ready to hear Washington's position regarding the non-deployment of missiles on Ukraine's territory, the dialogue would only be effective if the decision of the Budapest summit on Ukraine's possible NATO membership were revised.
Last month, Moscow presented its draft proposals on security guarantees for Russia, the US and NATO. One of the proposals suggests that NATO should end its eastward expansion and demanded that Ukraine be prevented from joining the alliance.