PITTSBURGH, United States, Sept. 25 (Xinhua) -- Brazilian President Luiz Inacio Lula da Silva said here Friday that assumptions that Iran is developing nuclear weapons should be backed by evidence.

    "We have to wait for the proof" that there is a nuclear plant in Iran, Lula said at a press briefing shortly after the conclusion of the two-day G20 summit in the U.S. city of Pittsburgh.

    The United States, Britain and France on Friday condemned Iran's alleged secret nuclear site and demanded its compliance with related UN resolutions, threatening sanctions if Iran failed to comply.

    Brazil's constitution forbids manufacturing of nuclear weapons, but the country supports using nuclear energy "for peaceful means," Lula said.

    If Iran or any other country develop nuclear energy for nuclear weapons, then "Brazil will be against it," he said.

    Isolating Iran will not help resolve the nuclear dispute, Lula added.

    Saying Brazil "is very comfortable with Iran," Lula said he planned to visit the country next year."

    "We have a very good trade relationship with Iran. We want to grow this relationship," he said.