Donald Trump promised to find a cure for cancer and eradicate Aids in America as he officially launched his 2020 re-election campaign.
The president made the remarks to a packed rally in Orlando where he was supported by the First Lady and senior White House staff.
The Republican's cancer pledge came in the wake of Democractic hopeful Joe Biden also vowing to cure cancer if he is elected.
Addressing the crowd in Orlando earlier in the night, Donald Trump Jr mocked the former vice president, who lost a son to cancer, for the promise.
However, it was unclear from the president's deadpan delivery whether he intended to do the same thing.
He told his audience: “We will come up with the cures to many many problems to many, many diseases including cancer.
"We will eradicate Aids in America and we’re very close. We will lay the foundation for landing American astronauts on the surface of Mars.”
Being cheered on by thousands, Trump also warned Democrats would change the US radically and legalise migrants coming across the southern border.
The Republican said his opposing party "want to destroy our country as we know it" and that it's "not going to happen."
Two dozen Democrats are competing for their party's nomination to face off against Trump in the November 2020 election.
Many of the top Democrats lead Trump in opinion polls in many battleground states.
"Just think what this angry left-wing mob would do if they were in charge of this country.
"Imagine if we had a Democrat president and a Democrat Congress in 2020.
"They would shut down your free speech, use the power of the law to punish their opponents," Trump said.
Trump made his re-election launch official at what was his 60th political rally since he took office in January 2017.
He brought his wife, Melania, and a large contingent of senior White House staff.
"Tonight I stand before you to officially launch my campaign for a second term as president of the United States," Trump said.
"I promise you I will never ever let you down."
During his speech, Trump declared himself a victim and aired his grievances.
He made an issue of Special Counsel Robert Mueller's investigation into Russian interference in the 2016 election.
The probe found insufficient evidence to establish that the Trump campaign engaged in a criminal conspiracy with Moscow.
It also described numerous attempts by Trump to impede Mueller's probe, but stopped short of declaring that he committed a crime.
"We went through the biggest witch hunt in political history," said Trump. "It was all an illegal attempt to overturn the results of the election."
Two-and-a-half years into his tenure, Trump sees plenty of positive factors, led by a growing economy with low unemployment.
"If the economy stays strong, he is very likely to get re-elected," said Trump confidant Newt Gingrich, a former Republican speaker of the U.S. House of Representatives.
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