NEW YORK • A United States prosecutor has attacked a claim by President Donald Trump's long-time personal lawyer Michael Cohen that many of the materials seized this week in Federal Bureau of Investigation raids on Mr Cohen's office and home as part of a criminal investigation should remain private.

Prosecutors also confirmed in a court filing last Friday that they have been investigating Mr Cohen for months, largely over his business dealings rather than his legal work.

Uncertainty over exactly what FBI agents seized from Mr Cohen comes as Mr Trump faces an intensifying probe by Special Counsel Robert Mueller into whether his presidential campaign colluded with Russia. The raids were partly a referral by Mr Mueller's office.

US District Judge Kimba Wood ordered Mr Cohen to appear in court tomorrow afternoon after holding three hearings on Friday into his request for a temporary restraining order blocking prosecutors from reviewing seized materials.

Assistant US Attorney Tom McKay accused Mr Cohen of invoking "wildly overbroad" claims of attorney-client privilege to avoid the disclosure of thousands of allegedly privileged communications related to the President and other cases.

These could include claims by Ms Stormy Daniels, the adult film star who claimed to have had a sexual encounter with Mr Trump in 2006.

Ms Daniels, whose given name is Ms Stephanie Clifford, wants to be freed from a non-disclosure agreement under which she was paid US$130,000 (S$170,500) shortly before the 2016 presidential election to keep quiet about that encounter.

Mr Cohen wants the judge to let his lawyers or a court-appointed "special master" review the seized materials to decide what can be turned over without violating his clients' rights to shield communications with their lawyers.

"We're pretty confident there are thousands of privileged communications," Mr Cohen's lawyer Mr Todd Harrison told the judge. But Mr McKay said "the attorney-client privilege can't at the same time be used as a sword and as a shield".

Prosecutors said it would be "unprecedented" to allow Mr Cohen's lawyers to decide what is privileged, and that the government should be allowed to use its own "taint team" or "filter team" to do the job.

FBI agents who conducted the raids were seeking information on payments to Ms Daniels and former Playboy model Karen McDougal, who also claims to have had a sexual relationship with Mr Trump, a person familiar with the matter said. Investigators have also looked for a possible broader pattern of fraud, tax evasion, money laundering and other crimes in Mr Cohen's private dealings, including his work for Mr Trump and real estate purchased by Russian buyers, the person said.

Mr Trump phoned Mr Cohen to "check in" last Friday, according to two people familiar with the call.

Depending on what was said, the call could be problematic for both men, as defence lawyers often advise their clients not to talk to each other during investigations.

Meanwhile, Mr Cohen on Friday filed for a 90-day delay in Ms Daniels' defamation lawsuit, citing last Monday's raids on his home, office and hotel room.

The subject of the defamation claim is a written statement issued by Mr Cohen in February, in which he said: "Just because something isn't true doesn't mean that it can't cause you harm or damage. I will always protect Mr Trump."

Ms Daniels says the statement portrays her as a liar, while Mr Cohen says it was hyperbole and, more importantly, accurate.

Mr Cohen had already notified the US District Court in Los Angeles on Thursday that he intended to request a stay in Ms Daniels' lawsuit against him and Mr Trump "on the grounds that an ongoing criminal investigation overlaps with the facts of this case".

Friday's motion said that because of that overlap, "Mr Cohen's Fifth Amendment rights may be adversely impacted if this case proceeds", a reference to the possibility that his testimony could be used by prosecutors to build a related criminal case against him.

Ms Daniels has until tomorrow to file her opposition to the stay, and then Mr Cohen will have until Tuesday evening to respond.

REUTERS, NYTIMES, BLOOMBERG