MADRID (NewsNation) — Russia’s invasion of Ukraine has sparked a “fundamental shift” in NATO’s approach to defense, and member states will have to boost their military spending in an increasingly unstable world, the leader of the alliance said Tuesday.

Secretary-General Jens Stoltenberg spoke as U.S. President Joe Biden and other NATO leaders began to arrive in Madrid for a summit that will set the course of the alliance for the coming years. He said the meeting would chart a blueprint for the alliance “in a more dangerous and unpredictable world.”

“To be able to defend in a more dangerous world we have to invest more in our defense,” Stoltenberg said. Just nine of NATO’s 30 members meet the organization’s target of spending 2% of gross domestic product on defense.

Biden will meet Turkish President Tayyip Erdogan at this week’s NATO summit in Madrid where the alliance will discuss the fallout of Russia’s invasion of Ukraine, the White House said in a statement on Tuesday.

Leaders at the Madrid summit will also take “historic decisions to strengthen the alliance’s collective defense and security,” the statement said.

Top of the agenda for leaders in meetings Wednesday and Thursday is strengthening defenses against Russia and supporting Ukraine.

The Associated Press and Reuters contributed to this report.