The United States is the "tip of the spear" in the fight against Islamic State and it would be difficult for the US-led coalition combating the group to be based in Iraq without an American presence, a State Department official said on Friday.
David Schenker, assistant secretary for the State Departments Bureau of Near Eastern Affairs, also told a news briefing in the United Arab Emirates that the United States would not accept any preconditions from Iran to engage in talks.