A US district judge is considering imposing tough limits on Apple for illegally collaborating with publishers to increase and fix the prices of ebooks.

Judge Denise Cote is deciding whether to prevent Apple for five years from signing deals with publishers which allow the iPad maker to reduce ebook prices.

"My focus is on making sure we don’t have collusive illegal activity again interfering with the ebooks market," Cote said.

However, Cote also said that she may not force Apple to use a court-appointed external monitor.

Last month she found Apple guilty of collaborating with major publishers to fix the prices of ebooks, creating unfair competition for other retailers.

As per the DOJ’s proposal, Apple would also have to appoint a permanent internal antitrust compliance officer for the next 10 years.