Speaking to reporters before boarding Air Force One at Joint Base Andrews, Trump suggested he would have skipped the gathering if it were being hosted elsewhere.

"If not for the fact that it was being held in Turkey by President Erdogan, I don't think I would've gone to it," Trump said. "I wouldn't have gone for what we went through over the last couple of months with the various countries."

The summit comes as Nato members prepare to discuss defence spending, regional security and ongoing conflicts in Europe and West Asia.

Defence cooperation in focus

Ahead of the trip, Trump signalled a significant shift in US-Turkey defence ties by notifying Congress of plans to move forward with the sale of General Electric F110 fighter jet engines to Turkey.

The engines are intended for Turkey's indigenous fifth-generation KAAN fighter programme.

Trump also indicated he is open to discussing Turkey's possible return to the F-35 fighter jet programme. Ankara was removed from the programme in 2019 after purchasing Russia's S-400 air defence system, triggering US sanctions and restrictions on defence cooperation.

When asked about his upcoming meeting with Erdogan, Trump said he hoped to make the Turkish leader "very happy."

Push for higher Nato defence spending

Despite his warm remarks about Erdogan, Trump is expected to press Nato allies to substantially increase defence spending.

The US administration wants member states to commit to raising defence budgets to 5 per cent of GDP over the next decade, arguing that European nations should shoulder a greater share of the alliance's security burden.

"President Trump fully expects that all allies will step up immediately and get on the path to 5 per cent," US Ambassador to Nato Matt Whitaker said ahead of the summit.

Trump also stressed that he expects greater commitment from America's allies, saying, "I just want their loyalty."