By Ken Dilanian and Tom Winter

WASHINGTON — The Mueller report's narrative of secret meetings between members of Donald Trump's orbit and Russian operatives — contacts that occurred both before and after the 2016 election — portrays a political campaign that left itself open to a covert Russian influence operation, former intelligence officials and other experts say.

While finding no criminal conspiracy, the report shows that Trump associates met with Russians after the intelligence community said in October 2016 that Russia was interfering in the presidential election, and even after the Obama administration announced a set of post-election sanctions to punish Russia for that behavior.

The 448-page report, written as a prosecutorial document, was not meant to assess, and does not say, whether U.S. national security was put at risk through those contacts. But former FBI and CIA officials and people who study Russian intelligence say the report describes a counterintelligence minefield — senior members of a presidential campaign and transition holding secret talks with a sophisticated foreign adversary, without the benefit of State Department and intelligence community counsel.

"The Russians came up against a group of people who were not intelligence savvy and who were predisposed not to listen to the intelligence and counterintelligence community," said Luis Rueda, who spent 27 years as a CIA operations officer. "The Russians made a very bold and aggressive attempt to take advantage of that — to try to compromise people, to try to leverage their access."

The FBI, as part of its counterintelligence mission, is continuing to investigate Russian attempts to influence the Trump administration and assess the national security damage from Russia's 2016 effort, current and former U.S. officials tell NBC News.