WASHINGTON (Reuters) - U.S. President Donald Trump said on Sunday he is ready to move to the second stage of sanctioning Russia, remarks suggesting that he is closer to ramping up sanctions against Moscow or its oil buyers in frustration over the war in Ukraine.

Trump has repeatedly threatened Moscow with further sanctions but withheld them as he pursued talks. The latest comments suggest an increasingly aggressive posture, but Trump stopped short of saying he was committed to such a decision or what such a second phase might entail.

Asked by a reporter at the White House if he is ready to move to the second stage of sanctions against Russia, Trump responded, "Yeah, I am."

Trump has been frustrated at his inability to bring a halt to the fighting in Ukraine after he initially predicted he would be able to end the war swiftly when he took office in January.

(Reporting by Trevor Hunnicutt; Writing by Ted Hesson; Editing by Ross Colvin and Lisa Shumaker)