Joe Biden invokes his late son's military service as he suggests Trump 'unfit to be president' over Russia claims

Joe Biden told reporters that Donald Trump "doesn't seem to be cognitively aware of what's going on" after allegations that the president had ignored intelligence briefings over a possible Russian-backed plot to offer bounties to Taliban-linked militia for the killings of US troops.

"The idea that he didn't know, or wasn't being briefed, that's a dereliction of duty," he said on Tuesday. "And if he was briefed, and didn't do anything, that's a dereliction of duty."

The presumptive Democratic nominee to face against the president invoked his late son Beau Biden, who served in the US Army during the Iraq War, imagining how his family would react to the allegations if he was serving in Afghanistan.

"I was talking to my wife Jill, and she doesn't get outraged often," he said. "She said, 'Joe, what would you have done if Beau was still in harm's way and this information came out?"

"It's an absolute dereliction of duty if any of this is true," he added. "The president has a lot to answer for and he should get the answers quickly."

If the allegations are true, then "unrelated to my running, this president is unfit to be president", he said.

The former vice president discussed the allegations during a press conference immediately following his remarks about the administration's response to the coronavirus.

On Sunday, following several reports revealing the scope of the intelligence and the failure of the White House to respond, Mr Biden called reports a "shocking revelation".

If true, he said, "then president Trump, the commander-in-chief of American troops serving in a dangerous theatre of war, has known about this for months ... and done worse than nothing."

The White House has denied that it had been briefed on the intelligence while also doubting the veracity of the intelligence and suggesting that media reports of the intelligence have compromised investigations.

On Monday, The New York Times reported that intelligence reports on the Russian scheme were in the president's daily briefs as early as February. While in office, Mr Biden said he would read his briefings every morning and again when he arrived at the White House.

Multiple reports through the president's term have indicated that Mr Trump doesn't read those reports and prefers oral briefings every few days.

House Democrats have warned that an information chasm between intelligence officials and the president could have significant foreign policy and military consequences, while GOP officials accused the media of printing the allegations in an attempt to undermine the president.

Mr Biden said that "at a minimum" the president must resolve the "discrepancy allegedly between the intelligence community as reported."

"Both parties should demand the facts," he said.