The White House national security adviser says the United States is “very sympathetic” to France in its dispute with Turkey over a naval standoff in the Mediterranean between the two Nato allies. The festering row has exposed Nato's struggle to keep order among its ranks, and its diminished US leadership under President Donald Trump. “Nato allies shouldn’t be turning fire control radars on each other. That’s not good,” National Security Adviser Robert O’Brien told reporters in Paris on Wednesday. He said Mr Trump was available to help defuse tensions, thanks to his personal relationships with Turkish President Recep Tayyip Erdogan and French President Emmanuel Macron. According to French accounts of the June 10 incident, the frigate <em>Courbet</em> was illuminated by the targeting radar of a Turkish warship that was escorting a cargo ship. France said it was acting on intelligence from Nato that the civilian ship could be involved in trafficking arms to Libya. The <em>Courbet</em> was part of the alliance's Operation Sea Guardian, which helps provide maritime security in the Mediterranean. Turkey’s foreign minister accused France of lying, and Turkey’s ambassador to France said the French navy was harassing the Turkish convoy. “We are very sympathetic to the French concerns,” Mr O’Brien said, while acknowledging differing accounts of what happened. “We’re taking it very seriously.” Mr Macron has also accused Turkey of flouting its commitments by ramping up its military presence in Libya and bringing in extremist militias from Syria. The United States is by far the most influential of the Nato allies, but has played a less prominent role under Mr Trump, who has publicly berated European members and Canada for not spending enough on defence budgets. Mr Trump has threatened to take US troops out of Germany without consulting allies, and has pulled out of multiple international agreements that Europeans regard as important to their security.