Relations between two of NATO's biggest partners are frayed over Syria, and the state of the free press in Turkey. The government recently seized the country's largest newspaper, and charged two journalists with treason.
Turkish President Recep Tayyip Erdogan was to attend a two-day nuclear security summit being held in the US capital at a time of fraught relations between Ankara and Washington and questions about whether the countries' leaders would even meet.
Disagreements between two key NATO allies have been increasing amid growing differences on policies towards Syria, a rebel Kurdish faction and Turkey's clampdown on the free press.
Turkey considers the PYD to be partners of the outlawed Kurdistan Workers Party (PKK), a separatist group seeking to carve out an autonomous Kurdish state across Turkey, Syria, Iraq and Iran.
"The relationship between the US and Turkey is strained generally because of the differing priorities of the two allies in Syria and more specifically due to their perceptions of the PYD," said Ozgur Unluhisarcikli, Ankara Office Director of the German Marshall Fund of the United States.
He said Turkey and the United States were "stepping on each other's toes" in Syria.
Crackdown on the free press
Turkey's relations with the US, as well as European allies, have also been strained by Ankara's clamp down on the free press.
Earlier this month the Turkish government seized control of the country's largest newspaper - Zaman. And just last week he lashed out at western diplomats for attending the opening of a treason trial against two journalists from the Cumhuriyet newspaper.
US State Department spokesman John Kirby effectively shrugged, "We don't always agree on everything - media freedom is one of them," he said.
Besides the security summit, Erdogan will preside over the grand opening of a large Ottoman-style mosque in Maryland. He had hoped to be joined at the event by US President Barack Obama, but the White House declined.
Before departing Turkey Erdogan said he would meet with Obama during his visit to Washington, but it now appears that he will meet with Vice-President Joe Biden.