STRESA, Italy, May 23 (Reuters) - Reaching a comprehensive deal on how to mobilise revenues stemming from frozen Russian assets will not be simple, Italy's Economy Minister Giancarlo Giorgetti said on Thursday ahead of a G7 finance summit.

Finance ministers and central bankers from the Group of Seven wealthy democracies - the United States, Japan, Germany, France, Britain, Italy and Canada - will gather in the northern Italian lakeside town of Stresa on Friday and Saturday.

"Revenues from financial assets are to be used to repay a loan to be disbursed to Ukraine in one lump sum," Giorgetti told reporters, adding any deal would need to have a solid legal basis. (Reporting by Giuseppe Fonte and Gavin Jones)