NEW YORK – Did President Donald Trump's ex-personal lawyer Michael Cohen come clean about every crime he knows about?

Federal prosecutors in New York don't know for sure – and that's one reason they won't recommend leniency for the 52-year-old attorney at his sentencing Wednesday.

The uncertainty explains the contrast with the more forgiving sentence recommendation Washington-based special counsel Robert Mueller proposed for the attorney who once served as Trump's fixer.

Cohen met with the prosecutors from the Southern District of New York only when he knew he faced likely indictment, the prosecutors wrote in a sentencing memo filed Friday.

When they met, the prosecutors wrote, Cohen agreed to discuss only the participation of others in campaign finance violations to which he pleaded guilty in August.

He "specifically declined to be debriefed on other uncharged criminal conduct, if any, in his past," the prosecutors wrote. He declined meetings "about other areas of investigative interest."

"In order to successfully cooperate with this office, witnesses must undergo full debriefings that encompass their entire criminal history, as well as any and all information they possess about crimes committed by both themselves and others," they wrote.

Cohen, they said, did not undergo such debriefings.

As a result, the prosecutors wrote, Cohen is not officially a cooperating government witness – and is ineligible for a leniency recommendation from them.

They acknowledged that Cohen provided information to Mueller, who is investigating Russian interference in the 2016 presidential election, for which they said he deserves some credit. But they wrote that he should not be spared prison time, as he requested.

They urged U.S. District Court Judge William Pauley to sentence him to roughly 42 months – less than the 51 to 63 months indicated by federal sentencing guidelines but still a "substantial term of imprisonment."

Their recommendation stems from a long-standing legal protocol.

"Federal prosecutors are crystal clear that when a defendant begins the process of considering cooperation that it's an all-or-nothing proposition," said Robert Mintz, a former federal prosecutor.

Mintz, who served as deputy chief of the Organized Crime Strike Force Division for the District of New Jersey, has no involvement in the Cohen case. He's managing partner of the McCarter & English law firm in Newark, New Jersey.

Cooperating witnesses "don't have the ability to pick and choose the areas of potential criminal conduct they want to disclose to prosecutors," he said. "What Michael Cohen attempted to do here is to have it both ways."

Mueller, in his separate sentencing recommendation, said Cohen committed a serious crime by lying to Congress about plans to build a Trump Tower in Moscow.

Cohen cooperated with Mueller's Russia investigation and pleaded guilty to the lies late last month.

Based on the admission and the assistance, Mueller's legal team recommended that any prison term Pauley might impose for Cohen's lies be served concurrently with any sentence the judge orders for the case brought by the New York federal prosecutors.

The final decision rests with Pauley, a senior judge nominated to the federal bench by President Bill Clinton and confirmed in 1998.

More:Five bombshells from Cohen memos, including information he's given Mueller

Also:Feds: Ex-Trump lawyer Michael Cohen should get 'substantial prison term'

Related:From Trump fixer to Mueller informant: Timeline of Cohen's role in Russia inquiry

Cohen pleaded guilty in New York this month to campaign finance violations.

Prosecutors said he paid hush money at Trump's direction to buy the silence of former Playboy model Karen McDougal and adult film star Stormy Daniels.

The women said they had sexual affairs with Trump before he became president, claims that could have jeopardized his 2016 presidential campaign. Trump denied their allegations.

Prosecutors said the payments amounted to unrecorded campaign contributions that exceeded giving limits.

The New York prosecutors essentially endorsed Cohen's account of the payments in their sentencing memo. It is unclear what other evidence they have, if any, to corroborate Cohen's account, which would implicate Trump in the felonies committed by his attorney.

Cohen also pleaded guilty this month to income tax evasion and lying to federally insured banks.

Prosecutors said Cohen hid income from his accountant and the IRS to avoid paying more than $1 million in federal taxes and lied to banks about his income and liabilities as he sought loans.

In the case handled by Mueller's legal team, Cohen admitted he lied when he told congressional committees last year that planning for the Moscow construction project ended in January 2016 before the start of the Republican presidential primaries.

Cohen said the Russia construction discussions actually continued until roughly June 2016, at which point Trump was the presumptive GOP nominee.

Mueller's team said Cohen disclosed contact "in or around November 2015" from a Russian national who claimed to be a "trusted person" in the Russian Federation who could offer the Moscow construction project "synergy on a government level."

That's an earlier contact than was previously known publicly.

Trump announced his candidacy for president in June 2015.

Trump tweeted Monday that Cohen was "trying to get his sentence reduced." He again called Mueller's investigation a "witch hunt."

Trump attacked unnamed "Dems" for "wrongly" calling the hush money payments arranged by Cohen a "campaign contribution ... which it was not."

"But even if it was, it is only a civil case, like Obama's – but it was done correctly by a lawyer and there would not even be a fine," Trump tweeted. "Lawyer's liability if he made a mistake, not me."

He did not clarify what "civil case" of President Barack Obama he was referring to.

Follow USA TODAY reporter Kevin McCoy on Twitter: @kmccoynyc.