JOINT BASE ANDREWS, United States: US President Donald Trump on Thursday stepped up criticism of Brazil's "disgraceful" presidential election, declining to say whether he recognised leftist Luiz Inacio Lula da Silva's victory over right-wing ally Flavio Bolsonaro.

Senator Bolsonaro fled to the United States to start a self-imposed exile on Wednesday and insisted that he is his country's rightful leader despite his defeat in the presidential run-off.

"I think the election was a disgrace in Brazil," Trump told reporters when asked if he accepted incumbent Lula's victory, as the US leader headed on a midterms campaign trip.

"I don't want to comment on it right now, but I thought the election was a very great embarrassment to the people of Brazil," Trump added.