Former Vice President Joe Biden promised at a campaign event in Iowa on Tuesday that if he is elected president in 2020 , the United States would cure cancer.

The presidential hopeful whose eldest son, Beau Biden, died from brain cancer in 2015 at the age of 46 was speaking at a campaign event in Ottumwa, one of several that he had scheduled in the state.

Ive worked so hard in my career that, I promise you, if Im elected president, youre going to see the single most important thing that changes America: Were going to cure cancer, he said.

Biden has long made bold claims about the fight against cancer, and he announced his Cancer Moonshot campaign during former President Barack Obama s final State of the Union address.

As campaign promises go, the ambition of this one overlooks a lot of complexities of the disease like, for example, the fact that cancer is actually more than 100 diseases and therefore not likely treatable with a single cure-all. In his prepared statements for another event, Biden prodded President Donald Trump over his previous comments about the disease, noting that Trump thinks windmills cause cancer .