'Confidence in Turkey.' Obama
'Ongoing dialogue.' Erdogan
Britain's Financial Times newspaper quoted a senior official as saying that Obama told Turkish leader Recep Tayyip Erdogan that "some of the actions that Turkey has taken have caused questions to be raised on the Hill" referring to the US Congress.
These questions centered on "whether we can have confidence in Turkey as an ally," said the official.
But while he confirmed the two leaders spoke several days ago, White House spokesman Bill Burton denied that any "ultimatum" had been issued to Ankara.
"I really don't know where they would have divined that from," he said.
"The president and Erdogan did speak about 10 days ago and they talked about Iran and the flotilla and other issues related to that," Burton said.
"We obviously have an ongoing dialogue with them, but no such ultimatum was issued."
Erdogan wants to buy American drone aircraft to combat separatist Kurdish rebels after the US military withdraws from Iraq at the end of 2011, the Financial Times reported.
The rebel group, the Kurdistan Workers' Party (PKK), has bases in the mountains in the north of Iraq, near the Turkish border.
The United States voiced disappointment after Turkey voted against fresh UN sanctions on Iran, which the United Nations Security Council adopted in June.
Ankara argued that Tehran should be given a chance to carry out a nuclear fuel swap deal, brokered by Turkey and Brazil.
The paper quoted the unnamed official as saying congressional concerns over Turkey mean "that some of the requests Turkey has made of us, for example in providing some of the weaponry that it would like to fight the PKK, will be harder for us to move through Congress."
Relations between Turkey and Israel were thrown into crisis after an Israeli raid targeting Gaza-bound aid ships on May 31 that left nine Turks dead.
Obama called on Turkey to cool its rhetoric about the raid when he met Erdogan at the G20 summit in Toronto in June, said the FT.