Donald Trump heads to Ankara on Monday for a key Nato summit, with allies on edge as the irascible US President continues to fume at the defence alliance. The gathering takes place on July 7and 8 and will focus on defence spending, defence industry innovation and support for Ukraine. In a sign of friction likely to come, Mr Trump last week criticised the “ridiculous” situation in which Nato finds itself. “The United States spends more money on Nato than any other country, by far, to protect them, without getting any benefit from so doing,” Mr Trump wrote on Truth Social.He has criticised Nato allies since his first term in office over what he regards as their stubborn refusal to meet defence spending commitments. He wants Nato members to increase spending to 5 per cent of GDP. 'Tokens of support'The war in Iran is also likely to loom large over the gathering.Experts say European nations are trying to “turn the page” on Mr Trump's criticism and offer him tangible signs of support. He is furious that allies did not do more to back the US-Israeli war against Iran, and accused the alliance of being a “paper tiger”.The US and Iran concluded another round of indirect talks in Doha on Wednesday, with no apparent breakthrough towards a lasting agreement.The talks followed weeks of exchanges of fire and retaliatory strikes stemming from disputes over shipping routes in the Strait of Hormuz.Mr Trump has struggled to end the war, which he started alongside Israel on February 28, and to fully reopen the strait. He claimed the US did not need its allies' help and threatened to withhold US support for Nato.Nato Secretary General Mark Rutte met Mr Trump at the White House last month in an effort to ease tension. He praised Mr Trump's handling of the Iran war and highlighted increases in European defence spending and investment in the US.Mr Rutte said between 4,000 and 5,000 American aircraft had operated from US bases across Europe during the conflict.Experts have questioned Mr Trump's criticism, noting that Portugal, Germany and the UK were critical launch points and command-and-control centres for US operations.“The US simply couldn't have sustained the kind of campaign that it did without access to those bases,” said Daniel Kochis, a senior fellow in the Centre on Europe and Eurasia at the Hudson Institute.“The Secretary General will likely play up the role that Nato allies played in terms of sustaining the length and lethality of US action against Iran."During the summit, member states are expected to offer Mr Trump what experts describe as “tokens of support”, including commitments on mine-sweeping operations, naval escorts in the Strait of Hormuz or funding for reconstruction.Also in question is whether the US will follow through on threats to withdraw US troops and military assets from Europe. About 60,000 to 65,000 US troops are permanently stationed in Europe. The US also has F-35 and F-16 squadrons in the region. Ukraine supportDuring the summit, allies are set to announce a landmark $75 billion military and financial aid package for Ukraine during its war with Russia. The funding will be a major win for Mr Trump, who has sought to reduce US military support for Kyiv and push European allies to take more of the burden.“This summit will be a success – low bar, but still a success – if the President goes into Ankara feeling that he has gotten something from the alliance on defence spending and production, and sees European leaders stepping up for Ukraine,” said Torrey Taussig, a senior fellow at the Atlantic Council.Meanwhile, Turkey's President Recep Tayyip Erdogan, a key ally of Mr Trump, is also pushing for the US to sell him F-110 engines worth $700 million, and Ankara continues its quest to be allowed back into the F-35 fighter jet programme.Turkey was removed from the programme after buying Russian S-400 air defence systems.“The F-35 is going to take longer because those are heavy rocks to lift,” said Rich Outzen, a former military adviser to the US State Department. “The F-110s are easier because they're less politicised, less prominent in legislation, and there's an easier workaround.”