Sen. Mitt Romney said it’s hard to believe that President Trump encouraging Ukraine and China to investigate Joe Biden and his son Hunter is “anything other than politically motivated.”

“When the only American citizen President Trump singles out for China’s investigation is his political opponent in the midst of the Democratic nomination process, it strains credulity to suggest that it is anything other than politically motivated,” the Utah Republican tweeted Friday.

“By all appearances, the President’s brazen and unprecedented appeal to China and to Ukraine to investigate Joe Biden is wrong and appalling,” he added.

By all appearances, the President’s brazen and unprecedented appeal to China and to Ukraine to investigate Joe Biden is wrong and appalling. — Mitt Romney (@MittRomney) October 4, 2019

Trump has denied any wrongdoing after he urged Ukrainian President Volodymyr Zelensky to investigate the 2020 presidential candidate and his son in a July phone call that prompted a whistleblower complaint about Trump’s interactions with the country. Hunter Biden served on the board of a Ukrainian gas company while his father was vice president, which Trump has argued deserves to be investigated.

On Thursday, Trump suggested China should also look into the Bidens. The younger Biden is linked to a high-ranking Chinese businessman who was charged with global corruption and bribery by the Justice Department in 2017.

Trump’s allegations of corruption against the Bidens have been unsubstantiated.