"The question was whether we were ready to open our door [to other countries]. Some feared that enlargement would delude and weaken NATO and provoke Moscow. Just as at previous crossroads, it was not an obvious choice, it was not an easy decision, and it took time," Stoltenberg said on Tuesday.
The NATO summit kicked off in Washington on Tuesday and will run through July 11.
Despite prior pledges, NATO has progressively expanded eastward toward the Russian border, with Sweden and Finland becoming the bloc's most recent member states, citing regional insecurity sparked by the Ukraine conflict. Moscow has for years objected to NATO's continued expansion and military buildup near Russian borders. Ukraine's plans to join the military bloc were among the reasons why Russia launched its special military operation in February 2022, Russian President Vladimir Putin said.
During the summit, US President Joe Biden awarded Stoltenberg the US Presidential Medal of Freedom, the highest honor the US can give to a civilian.