WASHINGTON (AP) — Former President Donald Trump campaign adviser George Papadopoulos has been sentenced to 14 days in prison for lying to the FBI.

The sentence was imposed Friday in federal court in Washington.

He is the first former campaign aide to be sentenced in special counsel Robert Mueller's Russia investigation.

Papadopoulos apologized for his actions, telling a judge that he had made a "dreadful mistake" and was eager for redemption.

Prosecutors sought a sentence of up to six months, while defense lawyers asked for probation.

His case was the first to detail a member of the Trump campaign having knowledge of Russian efforts to interfere in the 2016 presidential election while it was ongoing.

Prosecutors say Papadopoulos' lies caused irreparable harm to the investigation and he did not provide substantial assistance.

His attorneys say he cooperated fully.

Later Friday, Trump tweeted, "No Collusion. A great day for America!" after the announcement of Papadopoulos' sentence.

Others associated with Trump's campaign, including former national security adviser Michael Flynn and deputy campaign manager Rick Gates, have accepted plea deals. They are cooperating with investigators and await sentencing.

Trump said earlier Friday that he did not know Papadopoulos.