Federal prosecutors have said longtime Trump confidant Roger Stone deserves a sentence of seven to nine years in prison for lying to congress and tampering with a witness related to his efforts to learn about hacked Democratic emails during the 2016 US presidential election.

The sentencing filing came after days of tense debate within the US attorney's office in Washington about the appropriate prison term for the sixth Trump associate convicted and last person indicted in Robert Mueller's investigation.

Frontline prosecutors, some previously with Mr Mueller's team, argued for a sentence for Mr Stone that was higher than some of their supervisors were comfortable with, according to two people familiar with the discussions.

A recommendation on the higher end prevailed, with prosecutors' filings citing federal sentencing guidelines that ratchet up in cases involving obstruction that impedes the administration of justice.

A sentence of 87 to 108 months is “consistent with the applicable advisory guidelines and would accurately reflect the seriousness of his crimes and promote respect for the law”, prosecutors Jonathan Kravis, Michael Marando, Adam Jed and Aaron Zelinsky wrote in a 22-page filing.

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Hours before the filing was due on Monday, the new head of the District of Columbia office, interim US attorney Timothy Shea - a former close adviser to attorney general William Barr - had not made a final decision on Mr Stone's sentencing recommendation, according to the people, who spoke on the condition of anonymity to discuss internal deliberations.

Disagreements among prosecutors about sentencing recommendations are not uncommon, especially when it comes to politically sensitive high-profile cases. It would have been unusual, however, for the US attorney's office to endorse a sentence below the guideline range after winning conviction at trial, according to former federal prosecutors.

The Justice Department declined to comment before filing on Monday.

Mr Stone was convicted by a jury in November of lying to congress and tampering with a witness. Mr Stone has been a friend and adviser to the president since the 1980s and was a key figure in Mr Trump's 2016 presidential campaign, tasked to discover damaging information on Democratic opponent Hillary Clinton.

Federal guidelines typically call for a sentence ranging from 15 to 21 months for first-time offenders convicted of obstruction offences, such as lying to congress, making false statements and witness tampering, as Mr Stone was.

The range ratchets up steeply, potentially to more than seven years in prison if the offence involved other factors such as threatening physical injury or property damage to a witness; substantially interfering with the administration of justice; or the willful obstruction of justice. Each was cited by prosecutors.

A seven-to-nine year term “will send the message that tampering with a witness, obstructing justice, and lying in the context of a congressional investigation on matters of critical national importance are not crimes to be taken lightly”, prosecutors wrote.

They added that “Roger Stone obstructed Congress's investigation into Russian interference in the 2016 election, lied under oath, and tampered with a witness. And when his crimes were revealed by the indictment in this case, he displayed contempt for this Court and the rule of law.”

Sentencing recommendations come from prosecutors and the defence team. US district judge Amy Berman Jackson will have the final word at Mr Stone's hearing on 20 February.

Bruce Rogow, attorney for Mr Stone, declined to comment, saying: “We are speaking only in our submission to the court.”

Mr Stone was found guilty on seven counts resulting from his September 2017 testimony to the House Intelligence Committee, which was investigating Russian interference in the 2016 election and the Kremlin's efforts to damage Ms Clinton's campaign.

Prosecutors said Mr Stone lied to the intelligence committee to conceal his central role in the Trump campaign's efforts to learn about computer files hacked by Russia and made public by the anti-secrecy group WikiLeaks. He also threatened a witness who was an associate in an attempt to prevent the man from cooperating with politicians.

Lawyers for Mr Stone have said that his statements to the house panel were voluntary and that he believed questions about what he deemed unproven allegations of Russian interference were outside the probe's jurisdiction.

Mr Stone's two-week trial in November refocused attention on the Trump campaign's keen appetite for dirt on its political opponents, including testimony by former 2016 deputy campaign manager Rick Gates, who testified that he overheard a July 2016 phone call in which Mr Trump seemed to discuss WikiLeaks with Mr Stone.

The trial also highlighted Mr Trump's ongoing standoff with congressional Democrats then conducting an impeachment inquiry into how the president pressured Ukraine to bolster his 2020 reelection bid. Mr Trump directed the White House to withhold documents and block testimony in the inquiry, which ended in a senate acquittal.

Prosecutors asserted at trial that Mr Stone thwarted congress because the truth would have “looked terrible” for Mr Trump and the campaign. Prosecutors said Mr Stone lied to protect the president from embarrassment.

They called as witnesses Mr Gates and Mr Trump campaign strategist Steve Bannon, who took over in August 2016 when Mr Gates's boss, Paul Manafort, was fired over his Ukraine ties. Mr Gates and Mr Bannon said the campaign viewed Mr Stone as a liaison to WikiLeaks who claimed - even before the Russian hacking was known - to have insight about its plans.

Mr Stone's defence repeated his position that there was “no collusion” with Russia, and portrayed its client as a hapless victim of the same swagger and duplicity that he practiced on others, burnishing his reputation as a political dirty trickster.

Prosecutors pointed to an email to Mr Stone from another acquaintance, conservative writer Jerome Corsi, saying: “Word is friend in embassy plans 2 more dumps . . . Impact planned to be very damaging.”

Mr Corsi referred to WikiLeaks founder Julian Assange, who had been living under house arrest at the Ecuadoran Embassy in London since 2012. Last year, he was expelled and jailed in Britain. The US government is seeking his extradition to face charges for computer intrusion and violating the Espionage Act by seeking classified information.

Mr Stone and Mr Corsi have denied having contact with WikiLeaks, saying they were guessing based on Mr Assange's public statements.

Mr Stone did not testify during the trial, which ended on 15 November. Instead jurors saw videos of his television appearances and heard audio of his testimony before the House committee.

District judge Amy Berman Jackson directed both sides on 3 February to address whether prosecutors might re-raise their request to immediately put Mr Stone behind bars or seek another punishment for what they termed his repeated violations of a court gag order.

Before the trial, Mr Stone posted a photo of Ms Jackson with an image of crosshairs next to her head on Instagram in February 2019. During his trial he purportedly appealed for a presidential pardon through Alex Jones, a conspiracy theorist who hosts the right-wing Infowars website.