WASHINGTON (AP) — President Donald Trump dismissed George Papadopoulos as a "liar" and a mere campaign volunteer, but newly unsealed court papers outline the former adviser's frequent contacts with senior officials and with foreign nationals who promised access to the highest levels of the Russian government.

They also hint at more headaches for the White House and former campaign officials. Papadopoulos is now cooperating with special counsel Robert Mueller as he investigates possible coordination between Russia and Trump's 2016 White House campaign.

Records made public Monday in Papadopoulos' case list a gaggle of people who were in touch with him during the campaign but only with such identifiers as "Campaign Supervisor," ''Senior Policy Advisor" and "High-Ranking Campaign Official." Two of the unnamed campaign officials referenced are in fact former campaign chairman Paul Manafort and his business associate Rick Gates. Both were charged with financial crimes in an indictment unsealed Monday.

The conversations described in charging documents reflect Papadopoulos' efforts to arrange meetings between Trump aides and Russian government intermediaries and show how he learned the Russians had "dirt" on Hillary Clinton in the form of "thousands of emails."

Though the contacts may not by themselves have been illegal, the oblique but telling references to unnamed people — including "Professor" and "Female Russian National" — make clear that Mueller's team has identified multiple people who had knowledge of back-and-forth outreach efforts between Russians and associates of the Trump election effort.

It's a reality that challenges the administration's portrait of Papadopoulos as a back-bench operator within the campaign, an argument repeated Tuesday by White House press secretary Sarah Sanders, who dismissed him as a "volunteer" with a minimal role.

In charging the 30-year-old Papadopoulos with lying to the FBI, Mueller's team is warning of a similar fate for anyone whose statements deviate from the facts.

"I think everyone to whom Mueller and his team wanted to send a message heard loud and clear the message," said Jacob Frenkel, a Washington defense lawyer.

The White House had braced over the weekend for an indictment of Manafort and for allegations of financial misconduct that it could dismiss as unrelated to the campaign or administration. Then came the unsealing of Papadopoulos' guilty plea and an accompanying statement of facts that detailed his efforts to set up a meeting between Trump and Russian President Vladimir Putin, and his cooperation with prosecutors since his arrest at an airport last summer.

The extent of the contacts is substantial. During a six-month period ending Aug. 15, Papadopoulos met, telephoned, Skyped or emailed his three foreign contacts or five different Trump campaign officials a total of 29 times. He also traveled twice to London and once to Italy. Another trip to Moscow was canceled.

There are clear indications prosecutors used Papadopoulos to gather more information about the campaign as they probe possible criminal activity.

He was arrested in July, but the case was not unsealed until Monday, giving prosecutors weeks to debrief him for information and use him to get deeper into the campaign. He was initially arrested on false statements and obstruction of justice allegations, but as part of a plea deal, pleaded guilty only to lying to the FBI, a possible token of leniency in exchange for further cooperation.

In court papers, prosecutors have said prematurely making the case public would hurt his ability to be a "proactive cooperator," which legal experts say could include surreptitious techniques like wearing a microphone to record conversations.

"I would infer from that that he was working proactively on behalf of the prosecutors, which would mean going out and obtaining evidence," said former Justice Department prosecutor Peter Zeidenberg.

Though the campaign officials and other people referenced in the complaint are not named, it's nonetheless possible to ferret out the identities of several.

For instance, Joseph Mifsud is the "London professor" who figures prominently in the case, according to a comparison of court papers and emails obtained by The Associated Press. Mifsud confirmed to The Telegraph newspaper that he is the professor mentioned as a would-be link between the Trump campaign and Russia.

In court papers, Mifsud is described only as a "London professor" who met repeatedly with Papadopoulos and offered to set up meetings with Russian officials who could provide "thousands of emails" with damaging information about Clinton.

The professor is also credited in the document with introducing Papadopoulos to a woman referred to as a "female Russian national" who served as a potential link to the Russian government. Papadopoulos described her incorrectly in emails to Trump campaign officials as Putin's niece. She has not yet been identified publicly.

Mifsud, a vocal Putin backer, told the newspaper the FBI case lacks credibility and that he did not tell anyone he could produce emails that would weaken the Clinton campaign.

Papadopoulos' place on the Trump campaign was formalized in March when Trump adviser Sam Clovis released the names of eight foreign policy advisers amid public pressure on Trump to disclose his foreign policy team.

A lawyer representing Clovis confirmed in a statement that he was the person, identified as the "Campaign Supervisor" in court papers, who brought Papadopoulos onto an advisory committee on national security. In court papers, the unnamed supervisor receives some of Papadopoulos' email exchanges about his attempts to line up a meeting with the Russians, appearing to encourage the effort at one point by responding "Great work." He also later encouraged Papadopoulos to travel to Russia on his own.

The lawyer's statement said Clovis opposed any trip to Russia for Trump or his campaign staff but noted that Clovis may not have made his opposition known when "a volunteer made suggestions on a foreign policy matter."

The foreign policy advisory council on which Papadopoulos sat met on a monthly basis throughout the spring and summer for a total of about six times, according to an official involved with the group. Papadopoulos, who was based in London at the time, did not attend all of the meetings, but he did attend a dinner meeting of the advisers in late June at the Capitol Hill Club in Washington with Attorney General Jeff Sessions.

Trump released a photo of the meeting on social media.

Papadopoulos, who had no formal responsibilities, communicated most with Clovis and Manafort, according to an official involved with the group who was unauthorized to disclose internal campaign activities. Papadopoulos angered some on the foreign policy team in early May by urging former British Prime Minister David Cameron to apologize after calling Trump "divisive, stupid and wrong."

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Associated Press writers Steve Peoples in Washington and Greg Katz in London contributed to this report.