GENEVA, June 15 (Reuters) - The countries of the Gulf Cooperation Council are proposing to put a 31 percent safeguard tariff on imports of flat-rolled products of iron or non-alloy steel, they said in a filing published by the World Trade Organization on Thursday.

"The date of introduction of the measure will be determined in the TSAIP-Official Gazette which will be published once the Ministerial Committee approves the imposition of the measure," the filing said.

The tariff would last for three years and would fall to 28 percent in the second year and 25 percent in the third year.

(Reporting by Tom Miles; Editing by Toby Chopra) ((tom.miles@thomsonreuters.com; +41 58 306 2006; Reuters Messaging: tom.miles.reuters.com@reuters.net))