Turkey will boycott meetings with the US ambassador to Ankara as it no longer recognises the envoy as the US representative in the country, President Recep Tayyip Erdogan said Tuesday, stepping up a diplomatic row.

"We have not agreed and are not agreeing to this ambassador making farewell visits with ministers, the parliament speaker and myself," Erdogan said of US ambassador John Bass, who is shortly to leave Turkey after being nominated the US envoy to Afghanistan.

"We do not see him as the representative of the United States in Turkey," he said at a news conference with President Aleksandar Vucic in Belgrade.

It is traditional for outgoing envoys in Turkey to make valedictory visits to bid farewell to top officials before leaving their posts.

Although Bass is expected to leave Turkey in the coming days, it is unprecedented in the history of Turkish-US relations for Ankara to say it no longer recognises Washington's ambassador.

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 non-immigrant visas from its missions in Turkey, prompting Turkish missions in the United States to hit back with a tit-for-tat step of their own.

Erdogan said the arrest, 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?" Erdogan asked.

"If they did not (put them there), then who put them there? No state would allow such agents to pose such a threat."

The US embassy has dismissed the allegations against the consulate staffer as "baseless".