Barcelona, Spain - Brazilian President Luiz Inacio Lula da Silva hit out at his US counterpart, Donald Trump, saying the US leader has "no right" to threaten other nations.

Lula's comments come after Trump this month threatened to commit genocide in Iran, saying that a "whole civilization will die" in if the country did not bow to his demands.

"Trump has no right to wake up in the morning and threaten a country," Lula told the Spanish daily El Pais.

"It is essential that powerful leaders take greater responsibility in maintaining peace."

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Lula and Trump stand on opposite sides on issues including multilateralism, international trade, and the fight against climate change.

Brazil-US relations remain strained, despite a meeting between the leaders last year that helped ease tensions and led to a reduction in trade tariffs.

Lula renewed calls for reform of the UN Security Council, including the removal of the veto held by five permanent members and the inclusion of more countries from Africa and Latin America.

"It is time to redefine the United Nations to give it credibility, otherwise Trump is right," he said, referring to the Republican's criticism that the post-World War II international system is no longer relevant.

Lula spoke to the newspaper ahead of a visit to Spain, where he is to meet Spanish Prime Minister Pedro Sanchez and attend a forum of progressive leaders.

Other attendees at the gathering in Barcelona on Saturday include Mexican President Claudia Sheinbaum and South African President Cyril Ramaphosa.