MADRID (Reuters) - Spain formally requested on Monday European aid of up to 100 billion euros for its banks, the Economy Ministry said in a statement.

Spain's Economy Minister Luis De Guindos said in the letter to Eurogroup chairman Jean-Claude Juncker that the final amount of the financial assistance would be set at a later stage but

should be enough to cover all banks' needs plus an additional security buffer.

He also confirmed his intention to sign a Memorandum of Understanding for the package, which would include full details, by July 9.

(Reporting by Julien Toyer, editing by Paul Day)

(julien.toyer@thomsonreuters.com; Tel +34 91 585 21 59; Reuters Messaging: julien.toyer.thomsonreuters.com@reuters.net)