A US soldier accused of leaking a trove of secret files to WikiLeaks has offered to plead guilty to some but not all of the charges he faces in a pending court-martial, his defense lawyer said.

Bradley Manning, 24, "is not pleading guilty to the specifications as charged by the Government," his attorney, David Coombs wrote on his blog on Wednesday.

"Rather, PFC (Private First Class) Manning is attempting to accept responsibility for offenses that are encapsulated within, or are a subset of, the charged offenses," he wrote.

It was up to a military court to rule whether his plea was "legally permissible," and then government prosecutors would have to decide if they would continue to pursue all the charges against Manning, he said.

"PFC Manning is not submitting a plea as part of an agreement or deal with the Government," Coombs added.

The defense relayed the offer to a military judge at pre-trial hearings being held at Fort Meade, Maryland on Wednesday and Thursday.

By making the offer, Manning indicated he was ready to plead guilty to passing government information to WikiLeaks, though it was unclear if he would admit to passing all the files cited by prosecutors.

If the plea is deemed legal by the court, it could potentially simplify the trial, which is due to start on February 4, 2013, and possibly shield Manning from being convicted on more serious federal offenses related to computer fraud and the Espionage Act.

Manning had the option of being tried by a military jury but he informed the court he preferred to be tried by a judge only, according to Coombs.

Arrested in May 2010 while serving as an army intelligence analyst near Baghdad, Manning is charged with leaking classified military intelligence files on Iraq and Afghanistan and about 260,000 cables from the State Department.

The publication of the sensitive files by the secret-spilling WikiLeaks website caused huge embarrassment to Washington and angered US allies.