WASHINGTON, Jan 20: US President Barack Obama and Turkish President Tayyip Erdogan spoke by phone and pledged to deepen their cooperation in the fight against terrorism, the White House said in a statement. The two leaders also reiterated their shared goal of degrading and ultimately destroying Islamic State, the statement said yesterday. Obama condemned the recent string of attacks by the Kurdistan Workers Party against Turkish security forces and stressed the need for de-escalation, the White House said. (AGENCIES)