Former President Barack Obama endorsed the prime minister of Canada Justin Trudeau but has yet to express his support for former Vice President Joe Biden’s race to the White House and speak out on Biden and his son’s Ukraine scandal.

“I was proud to work with Justin Trudeau as President. He’s a hard-working, effective leader who takes on big issues like climate change. The world needs his progressive leadership now, and I hope our neighbors to the north support him for another term,” Obama wrote in a Tweet on Wednesday, Oct. 16.

Since Joe Biden announced his long-shot presidential bid, Obama has never openly discussed the issue. Biden then told reporters in April that he asked Obama not to endorse him.

The former president of the United States also keeps a distance from controversies regarding his closest associate’s international corruption allegations.

The Bidens are facing extensive scrutiny over Hunter Biden’s lucrative position in Ukrainian and Chinese companies while his father was vice president. Joe Biden has been accused of lying about his son’s business dealings and pressuring the Ukraine government to remove a prosecutor who was investigating the CEO of his son’s company.

In the fateful July 25 phone call, President Trump asked Ukrainian President Volodymyr Zelenskiy to look into Joe Biden and his son’s corruption allegations. An unknown whistleblower who was not on the call, alleged the president abused the power of his office to interfere in the 2020 election, triggering House Democrats to launch an official impeachment inquiry.

During a deposition in the House Democrats’ impeachment investigation on Wednesday, Oct. 16, George Kent, Deputy Assistant Secretary of State testified that the Obama administration was aware that the Ukrainian company that Hunter Biden sat on the board for was corrupt, as reported the Breitbart News.

President Trump suggested in June that “there has to be some reason” for Biden not being endorsed by the former president.

“How [former Vice President Biden] doesn’t get President Obama to endorse him—there has to be some reason why he’s not endorsing him,” Trump told Hill.TV. “He was the vice president. They seem to have gotten along. And how President Obama’s not endorsing him is rather a big secret. Then he goes and lies and said, ‘I asked the president not to endorse me.’ Give me a break.”