Tim Kaine receives his first intelligence briefing as a vice-presidential candidate
Kaine's Republican rival, Mike Pence, is expected to receive a similar classified briefing Friday, according to the same intelligence official and a source from the Trump campaign.
Donald Trump, the Republican presidential nominee, has already been given two intelligence briefings. His Democratic opponent, Hillary Clinton, has had one.
Surrogates and supporters from both parties have argued that neither Trump nor Clinton should receive such briefings - because of lingering questions surrounding Clinton's email scandal, and because of Trump's controversial musings on the campaign trail.
In Kaine's case, the Virginia senator - who is also a member of the Senate Foreign Relations and Senate Armed Services Committees - may only get one such intelligence briefing before the November election, NBC News reported.