U.S. says open to further talks with Iran about Iraq

(Adds quotes, details, background) WASHINGTON, June 17 (Reuters) - The U.S. State Department said on Tuesday that it is open to further talks with Iran about the instability in Iraq but that any such discussions are likely to take place at a lower level. U.S. Deputy Secretary of State Bill Burns met with Iranian officials briefly on Monday on the sidelines of wider talks in Vienna between Iran