Istanbul, Turkey (CNN) Turkish President Recep Tayyip Erdogan has launched a new tirade against the US, criticizing its support for Kurdish fighters in Syria and accusing the country of "sheltering a terrorist."

In a scathing address to regional governors in Ankara, Erdogan accused the US of sacrificing its years-old relationship with Turkey.

The speech appeared to dash hopes for a speedy end to the dispute between the two countries, which have been at loggerheads since the arrest of a US consular staff member just over a week ago. Metin Topuz, a Turkish national who works for the US consulate in Istanbul, is the second US mission staff member in Turkey to be detained this year.

Both sides have frozen many visa services in each other's countries and Erdogan said he would no longer recognize the authority of US Ambassador John Bass , whom he blames for the breakdown in relations.

"The decision of the US embassy and the statements that followed are neither fair nor truthful," Erdogan said in the capital, Ankara, on Thursday.

He slammed Washington for giving "weapons for free to a terror organization," a reference to the Kurdish YPG, a key US ally in the fight against ISIS in Syria.

He claimed the US had sent 3,500 trucks of weapons in to Syria, including heavy arms, saying they were being used by the YPG "to encircle us from the south."

The US has long supported the YPG and began openly supplying arms to it this year. The YPG is the backbone of a larger coalition of rebels that the US is backing to drive ISIS from Syria.

Ankara is worried that the Kurds may make territorial gains near the Turkish border if ISIS is finally flushed out of the area.

In Washington, State Department spokeswoman Heather Nauert responded to the accusations, and challenged the Turkish government to provide any evidence to support the allegation that the two employees engaged in terrorism. She also called on Turkey to give the staffers access to their attorneys.

Nauert said the US government has "some very real concerns" about the handling of these cases, and suggested the government might be trying to subvert US-Turkey law enforcement cooperation by detaining the employees, who were working in an office tasked with that issue.

"We hope Turkey is not trying to create distance between us and them on that," she said.

Gulen: Erdogan's adversary

The relationship between the US and Turkey has been on a downward spiral since a failed coup in 2016. Erdogan and his government blame Muslim cleric Fethullah Gulen for orchestrating the coup attempt and have repeatedly pushed Washington to extradite him from the US.

The Turkish government blames Fethullah Gulen for orchestrating the failed coup.

Turkey accuses Topuz, the arrested consular employee, of having ties to the Gulenist network, which Turkey considers a terrorist organization.

The Istanbul Chief Prosecutor is seeking a third US consular staff member for questioning and has accused him of hiding in the US consulate.

"On the one hand you're going to say 'I'm the native home of democracy,' on the other hand you are going to shelter a terrorist," Erdogan said. It was not clear if he was referring to Gulen or the third consular employee.

Bass denied any knowledge of a third employee being sought.

Erdogan also touched on the sensitive issue of an American pastor, Andrew Brunson, who has been detained in Turkey for more than a year.

He said that the pastor had obvious links to Gulenists. Erdogan even suggested two weeks ago that the two men could be swapped, raising concerns that Brunson may have been detained as a bargaining chip.

Erdogan targets Obama officials

Erdogan also took a second shot at the US Ambassador, blaming him for the latest troubles.

"Honestly speaking, it is the ambassador here who instigated this incident. It is not acceptable that the USA is sacrificing its relations with its strategic partner Turkey for an irresponsible ambassador. We can not accept this," he said.

Bass complained this week that Turkey had given the US no explanation as to why its consular staff members were detained. He also suggested Turkish officials were trying to purposely disrupt relations.

Erdogan -- who spoke of warmer relations with the US when Donald Trump was elected president -- seemed to throw that accusation back at the US, suggesting that officials left over from the Obama administration were trying to rattle the Turkey-US relationship.

"Unfortunately, a clique from the past administration that is within the American government wants to bring down an ax on relations between Turkey and the current US administration," he said.