The deal now goes to the Organisation of Economic Co-operation and Development (OECD), which is overseeing two days of talks starting Wednesday to find a consensus among 139 countries.
Washington on Thursday offered to accept a rate of at least 15% during international negotiations, significantly below its proposed 21% minimum for US multinational firms.
"The possibility of reaching a global and consensus-based solution is now concrete," Italian Economy Minister Daniele Franco said in a statement.