MILAN, July 14 (Reuters) - The European Union has already prepared a list of tariffs worth 21 billion euros ($24.52 billion) on U.S. goods if the two countries fail to reach a trade deal, Italy's Foreign Minister Antonio Tajani said in a newspaper interview on Monday.

U.S. President Donald Trump on Saturday threatened to impose a 30% tariff on imports from Mexico and the EU starting on Aug. 1, after weeks of negotiations with major U.S. trading partners failed to reach a comprehensive deal.

Tajani also told daily Il Messaggero that to help the euro zone economy the European Central Bank should consider a new "quantitative easing" bond-buying-programme, and more interest rate cuts.

($1 = 0.8565 euros)

(Reporting by Cristina Carlevaro, editing by Gavin Jones)

((cristina.carlevaro@thomsonreuters.com; +39 06 80307729;))