TOKYO, Aug 8 (Reuters) - The 10-year U.S. Treasury yield hit a 14-month low as news that President Barack Obama had authorised air strikes in Iraq added to already simmering geopolitical tensions and fanned demand for safe haven assets.

The 10-year yield declined to as low as 2.38 percent, the lowest since June 2013.

Speaking after meetings with his national security team, Obama - in his most significant response to the Iraq crisis - said he approved limited use of American air power to protect American personnel if Islamic State militants advance toward the Kurdish capital Arbil where they are based.

(Reporting by Shinichi Saoshiro; Editing by Jacqueline Wong)