ANKARA, Turkey (AP) — NATO Secretary-General Mark Rutte on Monday demanded that members put forward “clear, concrete and credible plans” to reach the organization’s defense spending targets at its annual summit in Ankara.

Rutte spoke in the Turkish capital ahead of the two-day summit starting on Tuesday at a crucial time for the alliance, with the United States scaling down its security role in Europe. Washington has been pressing allies to shoulder more of the spending burden.

The 32 nations agreed last year to invest 5% of their gross domestic product on defense — 3.5% on their defense budgets and 1.5% on roads, bridges and ports so troops and equipment can move faster in times of conflict.

Spain endorsed the goal but said it could fulfill NATO’s security requirements without spending so much. Some countries are still struggling to meet the alliance’s old target of 2% of GDP.

Asked what would happen to members that don’t have a clear plan, Rutte said: “If one or two of them still have to be convinced, we have ways to do that.” He did not elaborate.

U.S. Ambassador to NATO Matthew Whitaker suggested last week that the U.S. has something in store for those who do not step up, but declined to say more.

“President (Donald) Trump fully expects that all allies will step up immediately and get on the path to 5% and do it with urgency,” Whitaker said.

On spending among European allies and Canada, Rutte said that “the evidence we see so far is impressive.” He said NATO estimates that they will invest a combined $258 billion more in defense in 2025 and this year than they have in previous years.

But the numbers might not be enough to satisfy the Trump administration. Trump has repeatedly lashed U.S. allies over defense spending, and in the past threatened not to come to the defense of any member not doing enough — challenging NATO’s key reason for existence.

Trump also has called for “loyalty” from NATO allies, after some of them declined to allow the use of their military bases in the U.S.-Israeli war on Iran. As well as airing grievances about how much the U.S. spends on defense compared with other countries, Trump has sparred with allies over the war, his comments about annexing Greenland and other tiffs.

The Trump administration is promoting what it calls “NATO 3.0,” a vision in which Europe assumes greater responsibility for its own defense, freeing the U.S. to concentrate on other priorities. The approach was laid out earlier this year by Elbridge Colby, a U.S. undersecretary of defense, during a meeting of NATO defense ministers.

“We need our allies in NATO to step up and assume leadership roles, and I mean that not only in sort of loud cheerleading but also the moral authority and the moral compass of the alliance,” Whitaker said last week.

Some European governments have warned that Russia might be preparing a hybrid attack somewhere on the continent as Russian President Vladimir Putin struggles to secure victory in Ukraine.

NATO on Tuesday is due to make announcements showcasing the military equipment being bought with billions of dollars more being spent on defense and security. The event has been dubbed the “big reveal.”

Among the projects, many of them prepared and signed long before the summit, is one to replace NATO’s aging fleet of surveillance planes.