President Recep Tayyip Erdoğan has vowed that Turkish officials will boycott the US ambassador, deepening one of the worst rifts in decades between the Nato allies.

Erdoğan said he no longer regarded outgoing envoy John Bass as the US representative to Turkey after American missions in the country stopped issuing visas.

The dispute erupted last week when Turkey arrested a Turkish employee of the American consulate on suspicion of links to the group blamed for last year’s failed coup.

In response, the United States stopped issuing visitor visas from its missions in Turkey, prompting Turkish missions to hit back with a tit-for-tat step of their own.

“We have not agreed and are not agreeing to this ambassador making farewell visits with ministers, the parliament speaker and myself,” Erdogan said.

“We do not see him as the representative of the United States in Turkey,” he added, speaking at a news conference with Serbian President Aleksandar Vucic in Belgrade.

Bass is shortly to leave Turkey after being named the US envoy to Afghanistan and it is traditional for outgoing envoys to make valedictory visits to top officials.

And, although Bass is in Turkey for only a few more days, it is unprecedented in the history of Turkish-US relations for Ankara to no longer recognise Washington’s ambassador.

Erdoğan said the arrest of the consulate staffer, based on evidence found by the police, shows “something is going on at the Istanbul consulate.”

“The US should evaluate one thing: how did those agents leak into the consulate?” Erdoğan said.

Some Turkish officials have long alleged a US hand in the coup attempt on 15 July last year, which Ankara blames on the US-based Muslim preacher Fethullah Gulen.

Washington has dismissed claims it was involved as a ludicrous conspiracy theory, and on Tuesday it said it has seen no evidence linking its Turkish employees to a plot.

“These actions were are deeply disturbing to us,” state department spokesman Heather Nauert said in Washington, urging Turkey to allow the detained men access to lawyers.

“We have not seen any evidence that indicates that our staff members were involved in what the government is accusing them of doing,” she said.

On Monday, Turkish prosecutors summoned another local employee working at the American consulate in Istanbul, the Anadolu news agency said.

The man is reportedly in hiding at the consulate but the Turkish authorities on Monday detained his wife and his son, and on Tuesday detained his daughter.

Turkish officials had expressed hope of a new page in Ankara-Washington relations under President Donald Trump after bickering in the last months of Barack Obama’s term.

So far, Erdoğan has been careful not to take aim at Trump during the dispute, putting the blame squarely on Bass.

He said that if the order to suspend visa issuance came from Bass, then the US administration “should not keep him here one more minute”.

“They need to ask him, How can you break relations between the United States and Turkey, who gave you this authority?” he demanded.

But Nauert responded that Bass had been operating with the full authority of the US government.

The row between Turkey and the US has spilled out of the diplomatic sphere into the sporting world after American WNBA players Emma Cannon and Brionna Jones were denied visas for entry into Turkey with their Russian team.

“I think this situation will hurt a lot of teams in the long run,” texted Cannon, who plays for the Phoenix Mercury in the WNBA season. “I’m not happy about missing my first Euroleague game, and not be there for my teammates. But this is something way bigger than basketball, so I will cheer on my team and get ready for the next game.”

