NATO foreign ministers are meeting in Brussels on March 31 for talks expected to focus on defense spending and the fight against terrorism.
Speaking ahead of the meeting, Stoltenberg said the NATO ministers would discuss "fair burden sharing to keep the transatlantic bond strong" and "stepping up NATO efforts to project stability and fight terrorism."
Meeting with NATO foreign ministers for the first time, U.S. Secretary of State Rex Tillerson said NATO members must ensure that the alliance has "all of the resources, financial, and otherwise, that are necessary for NATO to fulfill its mission."
"We want to discuss how we can build on NATO's already important involvement in the fight to defeat [Islamic State] and other counterterrorism actions that NATO can provide," he also told reporters.
Tillerson initially planned to skip the NATO meeting, citing various commitments including a trip to Russia, forcing the allies to reschedule the event.
The gathering is preparation for a May 25 NATO summit, which President Donald Trump has said he will attend.
Since his election campaign, the U.S. president has pushed to the country's allies to increase their defense spending to help ease the burden on Washington.
Trump's criticism of NATO -- calling it "obsolete" at one point -- and his long-stated desires to have closer relations to Russia have concerned many NATO allies.
Stoltenberg dismissed concerns that Trump is not as committed as his predecessors to the Western military alliance and described ties between European members and the United States as "rock solid."
Some leaders are also concerned about Trump's commitment to end Russian interference in Ukraine.
Tillerson said he would raise the matter of "NATO's posture in Europe, most particularly in eastern Europe in response to Russia's aggression in Ukraine and elsewhere."
A senior State Department official said Tillerson would discuss ways of getting Russia to comply with the Minsk agreement, which set out steps to end the war between Kyiv and the separatists and restore Ukraine's control over its border with Russia.
Stoltenberg said the alliance has "a united position on Russia: strong defense and deterrence combined with dialogue."
Ukrainian Foreign Minister Pavlo Klimkin is to join his NATO counterparts in the afternoon for a session of the Russia-NATO Council, which Stoltenberg described as "a strong sign of our continued commitment" to the country.
Western nations have imposed sanctions against Moscow for its illegal annexation of Ukraine's Crimea region and for Russia's support of separatist fighters in eastern Ukraine.
After a session of the Russia-NATO Council on March 30, Stoltenberg told journalists that the two sides "continue to have clear disagreement" on the crisis in Ukraine.
He said the alliance urged Moscow to use its influence with militants in eastern Ukraine to compel them to meet their obligations under the so-called Minsk process.
He added that NATO was firm in its support for Ukraine's sovereignty and territorial integrity.
"The allies do not and will not recognize Russia's illegal annexation of [the Ukrainian region of] Crimea," Stoltenberg said.
Russia's ambassador to NATO, Aleksandr Grushko, in turn criticized NATO for "continuing to provide political and practical support to Kyiv," a policy that he said is "at odds with genuine interests of conflict settlement."
With reporting by AP, AFP and The Los Angeles Times