Joe Biden, citing intelligence briefings, warns that Russia, China are engaged in election interference

"We know from before and I guarantee you I know now because now I get briefings again," the presumptive Democratic nominee said during an evening fundraiser. "The Russians are still engaged in trying to delegitimize our electoral process. Fact."

"China and others are engaged as well in activities that are designed for us to lose confidence in the outcome," he added.

Biden has warned in the past about Russian interference, but it was perhaps the former vice president's bluntest warning to date about a potential replay of the 2016 election.

The U.S. government in recent weeks has started briefing the presidential campaigns and the national parties about election threats from foreign adversaries, The Washington Post reported last month. The Office of the Director of National Intelligence is spearheading the effort, and National Counterintelligence and Security Center Director William Evanina is leading the briefings.

The briefings are done in coordination with the FBI, Department of Homeland Security and the intelligence community's election threats executive, Shelby Pierson, as part of the government's effort to secure the 2020 election, ODNI officials said.

But Biden said at a news conference on June 30 that he had not received a classified intelligence briefing. When asked amid reports that Russia had offered bounties to kill American troops in Afghanistan if he had requested that the Trump administration help provide intelligence briefings, he said, "They have not offered a classified briefing. And as this proceeds I may very well do that."

"If it doesn't get cleared up quickly, I will seek and ask if I can be briefed," he added.

It was not clear on Friday night when precisely the briefings had started.

Google announced in early June that Chinese and Iranian government hackers had targeted the Gmail accounts of staffers working on Biden and Trump campaigns. There were no signs that the accounts were compromised, according to the announcement from a Google threat analyst.

During the Friday evening fundraiser, Biden also reiterated that what concerns him the most is access to voting.

"Frankly, this is the thing that keeps me up most at night," Biden said. "Making sure everyone who wants to vote can vote. Making sure that the vote is counted, making sure we're all trusting in the integrity of the results of the election."

"Our campaign has undertaken a historic effort in both the commitment to and the attempt to provide for significant help to beat back voter suppression and every attempt at election interference," Biden added. "We only have a few months, so we've got to get this right."