The intelligence agencies warned the White House late last year that Russian intelligence officers were using President Trump’s personal lawyer Rudolph W. Giuliani as a conduit for disinformation aimed at undermining Joseph R. Biden Jr.’s presidential run, according to four current and former American officials.
The agencies imparted the warning months before disclosing publicly in August that Moscow was trying to interfere in the election by taking aim at Mr. Biden’s campaign, the officials said. Mr. Trump and Mr. Giuliani have promoted unsubstantiated claims about Mr. Biden that have aligned with Russian disinformation efforts, and Mr. Giuliani has met with a Ukrainian lawmaker whom American officials believe is a Russian agent.
Robert C. O’Brien, the national security adviser, presented the warning about Mr. Giuliani to Mr. Trump in December. Two former officials gave conflicting accounts about its nature. One said the report was presented to Mr. Trump as unverified and vague, but another said the intelligence agencies had developed solid and credible information that Mr. Giuliani was being “worked over” by Russian operatives.
Mr. Trump shrugged it off, officials said, but the first former official cautioned that his reaction could have been colored in part by other information given to him not long before that appeared to back some of Mr. Giuliani’s claims about Ukraine. The specifics of that material were unclear.