Turkish Prime Minister Recep Tayyip Erdogan unleashed a furious rant against the United States on Wednesday, holding America responsible for the “sea of blood” spilled in Syria and for supporting other terrorist organizations while focusing too intently on defeating the Islamic State.

CNN reports Erdogan was especially angry about U.S. military support for the Syrian Kurds. The Kurds have been vital U.S. allies on the ground against ISIS, but Erdogan, whose country is currently fighting Kurdish Turkish separatists, thinks the Syrian Kurds should be written off as terrorists themselves. They presented evidence alleging strong ties between the Syrian Kurds and the PKK to Vice President Joe Biden during his trip to Turkey last month.

The U.S. government has repeatedly refused to classify the Syrian Kurds as terrorists, most recently on Monday, with State Department spokesman John Kirby insisting that “Kurdish fighters have been some of the most successful in going after Daesh [Islamic State] inside Syria. We have provided a measure of support, mostly through the air, and that support will continue.”

This made the Turks angry enough to summon the U.S. ambassador in protest. “The State Department confirmed the meeting took place, but declined to describe the tone or subject of the meeting,” reports the Wall Street Journal.

Turkey has also strongly pushed for the overthrow of Bashar Assad in Syria, often asserting that much of the Syrian bloodbath, refugee crisis, and even the rise of ISIS could have been avoided if the West had taken military action against Assad long ago. The Syrian Kurds are dedicated foes of ISIS, but they are much more ambivalent about rebelling against Assad, to the frustration of Turkish leaders.

The degree of affiliation between the Kurdish YPG militia in Syria and the PKK separatists in Turkey is a matter of some debate, although Anakara increasingly sees them as joined at the hip. The Turks also worry that weapons from the Syrian Kurdish militia will find their way across the border, into the hands of PKK militants in Turkey.

CNN supposes the possibility Syrian Kurds and their PYD Party being invited into multi-party peace talks sparked Erdogan’s fury against the United States, a possibility that stokes Turkish fears of a Greater Kurdistan forming across territory in Syria, Iraq, and Turkey. Tensions are rising high enough to raise doubts about whether Turkey will continue allowing the U.S. to launch anti-ISIS airstrikes from the Incirlik airbase.

“How will we ever be able trust you? Am I your regional partner or are the terrorists in Kobani?” Erdogan snarled on Wednesday, referring to a meeting between U.S. envoy Brett McGurk and Kurdish leaders in the Syrian border city of Kobani.

“They do not say anything to our faces, but they make different statements elsewhere,” Erdogan said of U.S. officials. “It is not possible to understand what type of partnership this is.”

The Turkish leader is also feeling renewed pressure from Syrian refugees, with another 30,000 of them accumulating on the Turkish border.

“The refugees have fled an offensive by Syrian government forces and Iranian-backed militias, supported by Russian air strikes, on rebel-held areas around the divided northern city of Aleppo,” writes the BBC. “The International Committee of the Red Cross said the humanitarian situation in the Aleppo area is deteriorating rapidly as supply routes used for bringing in aid have been cut.”

The BBC adds that the current surge of fighting around Aleppo has killed at least 500 people over the past 10 days, including dozens of civilians, and displaced an estimated 50,000 people, in harsh weather conditions.

Turkish Prime Minister Ahmet Davutoglu accused the U.N. of being “two-faced” for telling Turkey to accept more refugees while allowing the Russians to continue bombing Aleppo, driving more people toward the Turkish border. He also said Turkey would become an accomplice to the Assad regime’s “ethnic cleansing” agenda by accepting another huge wave of refugees.

This came with another furious anti-U.S. rant from President Erdogan: “Are you on our side or the side of the terrorist PYD and PKK organisation? Is there a difference between the PKK and the PYD? Is there a difference with the YPG?”

“We have written proof!” Erdogan insisted. “We tell the Americans: ‘It’s a terror group.’ But the Americans stand up and say: ‘No, we don’t see them as terror groups.'”