WASHINGTON – In March 2016, when Trump campaign aide George Papadopoulos told candidate Donald Trump he could arrange a meeting with Russian President Vladimir Putin, Trump "nodded with approval," his defense team alleged in court documents filed Friday.

Papadopoulos was the first Trump aide to plead guilty in special counsel Robert Mueller's investigation into Russian interference in the 2016 U.S. presidential election.

In October, he admitted to lying to the FBI about his interactions with several Russians who had high-level connections to the Kremlin.

Prosecutors have called for a jail sentence up to six months. His defense team, in the 16-page memo to the court, argued that Papadopolous was "caught off-guard by an impromptu interrogation" when he lied to the FBI and called for leniency, preferably probation.

The defense team called his motives "wrongheaded indeed but far from the sinister spin the Government suggests."

At the critical March 31, 2016 meeting at Trump's hotel in Washington, Papadopoulos, according to his lawyers, was "eager to show his value to the campaign" by telling Trump and other campaign officials he had "connections that could facilitate a foreign policy meeting" between Trump and Putin.

"While some in the room rebuffed George’s offer, Mr. Trump nodded with approval and deferred to Mr. Sessions who appeared to like the idea and stated that the campaign should look into it," Papadopoulos' defense team stated in the documents.

At the time, Sessions — then a senator from Alabama and currently the attorney general — was a staunch Trump campaign supporter and adviser.

More:Mueller team wants Trump campaign adviser to spend up to six months in jail

Related:Who is former Trump campaign aide George Papadopoulos?

Before the March meeting, Papadopoulos' lawyers said, the young campaign aide had recently met with London-based professor Joseph Mifsud who, in turn, introduced him to a young woman named Olga, a purported relative of Putin.

It was shortly after meeting Olga that Papadopoulos proposed a Putin meeting to Trump and his campaign.

"To say George was out of his depth would be a gross understatement," his lawyers argued. "Nonetheless, George strived to organize a meeting with the Russian government and help the Trump campaign promote its foreign policy objective."

Defense lawyers acknowledge that Papadopoulos “lied, minimized, and omitted material facts” to the FBI about his foreign contacts, saying, “Out of loyalty to the new president and his desire to be part of the administration, he hoisted himself upon his own petard.”

In April 2016, during a breakfast conversation with Mifsud that Papadopoulos thought would finalize plans for a meeting with the Russian leader, the professor told him that "individuals in Moscow possessed 'dirt' on candidate Hillary Clinton in the form of 'thousands of emails,'" his lawyers wrote.

In lying to the FBI, prosecutors argued, investigators missed an opportunity to properly question Mifsud. "The defendant’s lies undermined investigators’ ability to challenge the professor or potentially detain or arrest him while he was still in the United States," they said, noting that the professor left the U.S. in February 2017 and has not returned.

In Friday's filing, however, Papadopoulos' lawyers wrote that "he does not, however, believe his false statements actually harmed the investigation as alleged."

Contributing: Brad Heath