UPDATE: At 5:30pm PDT, US Magistrate Sheri Pym agreed to cancel Tuesday's hearing and tentatively stayed an earlier order requiring Apple to assist the FBI in unlocking the iPhone. Apple did not object.

ORIGINAL STORY BELOW:

The Federal Bureau of Investigation said Monday that it might be able to break into the seized iPhone at the center of an encryption battle with Apple. That is why it wants a federal judge overseeing the litigation to vacate Tuesday's hearing on whether Apple should assist the authorities in bypassing the four-digit passcode on the iPhone used by San Bernardino terrorist Syed Farook, according to court documents filed Monday.

"On Sunday, March 20, 2016, an outside party demonstrated to the FBI a possible method for unlocking Farook’s iPhone. Testing is required to determine whether it is a viable method that will not compromise data on Farook’s iPhone," the government said.

US Magistrate Judge Sheri Pym has not yet ruled on the government's motion.

"We are waiting for the court to rule on the motion," said Thom Mrozek, a Justice Department spokesman in Los Angeles.

The government said in its filing that following the seizure of the iPhone in December, "the FBI did not cease its efforts after this litigation began" to break into the phone.

"As the FBI continued to conduct its own research, and as a result of the worldwide publicity and attention to this case, others outside the U.S. government have continued to contact the U.S. government offering avenues of possible research," the filing continued. The government did not name who provided the advice that it says might unlock the phone.

Last month, Judge Pym ordered Apple to code software to assist the authorities in breaking into the phone. Apple objected, saying it amounted to an encryption backdoor. Pym then scheduled a high-profile court hearing on the matter in Riverside County federal court. Among other things, Apple claimed that the order violated its constitutional rights of speech and due process. Pym had agreed with the government that the All Writs Act, a 1789 law, gave judges the power to issue orders, like the one in this case, despite the fact that there is no law on the books requiring such assistance.

Reuters, meanwhile, reported Tuesday that a group of US senators began circulating draft legislation that would give federal judges a clear legal basis to issue orders like the one in the Apple case.

The development came a day after it was reported that researchers discovered a flaw that could allow attackers to decrypt a small part of the iPhone operating system. This iMessage flaw, however, might be of little benefit to the FBI in pulling data from the iPhone. However, the bug underscores what security people have long known—cryptography is excruciatingly hard to get right, and common bugs often leave an opening for law enforcement agents and criminal hackers.

Hours before the government's filing, Apple CEO Tim Cook said during a live-streamed product launch event that "We did not expect to be in this position at odds with our own government. But we believe strongly that we have a responsibility to help you protect your data and protect your privacy. We owe it to our customers and we owe it to our country. This is an issue that impacts all of us."

(Ars Senior Business Editor Cyrus Farivar contributed to this report from Riverside, Calif.)