(Adds comments on Syria, background)
By Ezgi Erkoyun
ISTANBUL, June 12 (Reuters) - Turkey has already purchased S-400 defence systems from Russia and hopes they will be delivered in July, Turkish President Tayyip Erdogan said on Wednesday, an announcement likely to ratchet up tensions with NATO ally Washington.
Turkey and the United States have sparred publicly for months over Ankara's order for the S-400s, which are not compatible with NATO's systems.
"Turkey has already bought S-400 defence systems. It is a done deal. I hope these systems will be delivered to our country next month," Erdogan said.
U.S. acting Secretary of Defense Patrick Shanahan outlined last week how Turkey would be pulled out of the F-35 fighter jet programme unless Ankara changed course from its plans to purchase the S-400 missile defence system.
Turkey has criticised the letter from Washington and said it did not live up to the spirit of the NATO alliance. It is working on a response to be sent in the coming days, according to Turkish Defence Minister Hulusi Akar.
The United States says Turkey's acquisition of the Russian system poses a threat to Lockheed Martin Corp's F-35 stealth fighters, and has warned of potential U.S. sanctions if Ankara presses on with the deal.
Speaking at a meeting of his AK Party members, Erdogan said:
"We will call to account in every platform Turkey being excluded from the F-35 programme for reasons without rationale or legitimacy."
He noted that Turkey was also a manufacturing partner in the programme.
Turkey has repeatedly proposed a joint working group to assess the impact of the S-400 surface-to-air defence systems, but Washington has not yet taken up the suggestion.
Erdogan also said he wanted to talk about the issue on the phone with the United States, before he meets President Donald Trump in Osaka, Japan, at the end of this month.
Russia said on Tuesday it planned to deliver its S-400s to Turkey in July, setting the clock ticking on the U.S. sanctions threat.
Erdogan also discussed the situation at Turkey's border with Syria, pledging to sweep the YPG Kurdish militia from northern Syria, and east of the Euphrates, revitalising a plan put on hold after the United States said it would pull its troops out of the area.
"We may suddenly come one night," he added referring to previous military operations to Syria.
Turkey considers the YPG an enemy and has already intervened to oust the fighters from territory west of the Euphrates in military campaigns over the past two years.
Ankara has been infuriated by U.S. support for the YPG, which it considers a terrorist organisation and an extension of the outlawed Kurdistan Workers' Party (PKK), which has fought an insurgency in southeast Turkey for more than three decades. (Reporting by Ezgi Erkoyun in Istanbul; Additional reporting by Humeyra Pamuk in Washington; Writing by Ali Kucukgocmen; Editing by Frances Kerry and Peter Cooney)