UNITED NATIONS, Sept 25 (Reuters) - Brazilian President Luiz Inacio Lula da Silva said on Wednesday he is ready to sign a trade agreement between the European Union and South America's Mercosur bloc, but that it is now up to the EU to conclude negotiations.

Speaking on the sidelines of the U.N. General Assembly, Lula said his country was surprising investors and credit rating agencies with stronger than expected growth, and offering new stability now that tax reform has advanced in Congress.

"If the EU is ready we can sign the trade agreement during the G20 meeting in Brazil," he told reporters, referring to the Group of 20 rich nations summit in Rio de Janeiro in November.

"I have never been so optimistic about the EU-Mercosur accord," the Brazilian leader added.

A European diplomatic source said there had been progress towards resolving differences at a face-to-face meeting of negotiators in Brasilia on Sept 5-6.