Turkey is willing to hold off ratifying Sweden's bid to join NATO this month as it awaits signs of U.S. support for its own request to buy F-16 jets, sources said, potentially disappointing bloc allies hoping to end 17 months of delay. President Tayyip Erdogan elated a NATO summit in July by promising to send the bid to Turkey's parliament for ratification when it reopened in October, appearing to green-light Sweden after having raised objections over its alleged harbouring of terrorists.