The United States on Wednesday has rejected Russia's claims of Turkey buying oil from Daesh, calling the allegations 'preposterous', 'ridiculous' and 'untrue.'"We reject the premise that the Turkish government is in league with Daesh to smuggle oil. We have seen no evidence to support such an accusation," State Department spokeswoman Julia Mason said in a statement, while the White House said if the Russians are really concerned about Daesh's illicit finance they should take it up with Syria's President Assad."Turkey is taking steps to improve the security of its border with Syria, working with international partners. One goal of this effort is to cut off Daesh smuggling," Mason added.Pentagon spokesman Lt. Col. Steve Warren has also denied Russia's allegations about Turkey buying oil from the terrorist organization. "We absolutely flatly reject the notion that Turkey is working with ISIL" Warren said, using an alternative acronym for Daesh, via video conference from Baghdad and added that Turkey has been a great partner to the U.S. in the fight against Daesh."Any thought that the Turkish government is somehow working with ISIL is again, it's just preposterous, and completely untrue," he added.Josh Earnest, the Assistant to the President and Press Secretary in the White House has also dismissed claims and blamed Assad for exploiting Daesh oil."The irony of the Russians raising this concern is that there's plenty of evidence to indicate that the largest consumer of ISIL oil is actually Bashar al-Assad and his regime, a regime that only remains in place because it is being propped up by the Russians," said Josh Earnest. "If the Russians are really concerned about ISIL's illicit finance efforts, they should take it up with Bashar al-Assad, the person that is relying on the Russians for his continued ability to remain in power" he added.President Recep Tayyip Erdoğan and Prime Minister Ahmet Davutoğlu had strongly refuted Russia's allegations, while the former had challenged his Russian counterpart to step down if he cannot prove his claims.