Obama calls Letta to compliment for international work
U.S. president offers continued friendship after premier quits14 February, 19:58
Obama called Letta from Air Force One, Italian government sources said.
Letta resigned after 10 months at the helm of a weak, bickering left-right coalition government.
President Giorgio Napolitano is expected to give a government-formation mandate to the leader of Letta's Democratic Party (PD), Florence Mayor Matteo Renzi, who at 39 could become Italy's youngest premier.
Renzi effectively pulled the plug on Letta's executive when he requested the PD withdraw support at a party meeting Thursday so he could take the helm of a new one that would drag Italy out of the "quagmire".