ISTANBUL, March 6 (Reuters) - Turkey could retaliate against potential U.S. steel tariffs by hiking duties on imports of American cotton, one of President Tayyip Erdogan’s economic advisers said on Tuesday.

U.S. President Donald Trump said last week he would impose broad tariffs on imports of steel and aluminum to protect American national security, sparking concern from U.S. trade partners and causing turmoil in global stock markets.

“Starting with Turkey, countries affected by the U.S. tax imposition are preparing to answer the U.S. in alternative goods - such as Turkey in cotton,” Cemil Ertem, a prominent Erdogan adviser, wrote in the Milliyet newspaper.

He did not say how much of a tariff was being considered.

The Economy Ministry said it had spoken to European Union Trade Commissioner Cecilia Malstrom regarding the issue and that they had agreed to cooperate on it in the World Trade Organization (WTO).

Turkey, home to a major textile industry and companies that supply global fashion brands such as Zara, Adidas and Nike, imported $519 million worth of U.S. cotton in 2016, according to data from the Turkish Statistical Institute.

U.S. cotton accounted for 42 percent of its total imports that year, the biggest share of any country, the data showed.

Turkey is the world’s eighth-largest steel producer and the sixth-largest exporter to the United States. The reaction so far from Turkish steelmakers to Trump’s proposal has been relatively sanguine, with one saying it could ramp up its U.S. business in response.

An industry association has said Turkish steel producers could still remain competitive thanks to lower costs.

Trump’s proposal has also spurred talk of retaliatory duties from Europe, where officials have threatened counter-measures on Harley-Davidson Inc motorbikes, bourbon and jeans.

The U.S. president has also faced growing domestic pressure from political and diplomatic allies as well as American companies urging him to pull back from the proposed tariffs, although he has said he will not back down. (Reporting by Orhan Coskun and Ceyda Caglayan, Writing by Ali Kucukgocmen, Editing by David Dolan and Ed Osmond)