In a phone conversation, Tsipras said Greece had demonstrated it wanted an agreement, a government source said of the conversation, also reported by the state news agency ANA.
The premier was said to have told Lew a sustainable deal was one which "respects the Greek people and all of their sacrifices in the last five years".
Neither the source nor ANA said what Lew's response was.
The US treasury secretary has regularly added his voice to the debate in the eurozone about the Greek crisis, urging creditors to examine a restructuring of Greece's huge debt mountain.