Iraq's Kurds will maintain their plan to hold a referendum on independence on Sept. 25, despite a U.S. request to postpone it, a high-ranking Kurdish official told Reuters on Saturday.

"The date is standing, Sept. 25, no change," said Hoshyar Zebari, a close adviser to Kurdistan Regional Government President Massoud Barzani, commenting on the request communicated by U.S. Secretary of State Rex Tillerson.

The U.S. State Department said in June it was concerned that the referendum will distract from "more urgent priorities" such as the defeat of Islamic State militants.