Experts said yesterday that they expect the Pentagon this weekend to restore the communication links between the military's unclassified computer network and a comparable one used by research universities that it severed recently.

Until then, users on the two systems cannot communicate with each other, and the messages they try to send will be put on hold, bogging down the electronic communication channels, according to Clifford Stoll, a computer security expert visiting at Harvard.

The Pentagon broke off the communications links on Monday after learning that an intruder had broken into computers on the military network--known as Milnet--from a series of university systems, said a Pentagon spokesperson who refused to give her name.

The same message systems were slowed dramatically last month when the now-infamous "Cornell Virus," allegedly written by Robert T. Morris '87-'88, infected and disabled more than 6000 computers by spreading itself through the university network, called Arpanet, to Milnet. Unlike the effects of the virus, though, the Pentagon's action has not significantly disrupted the Arpanet operation.

The computer community is generally displeased with both the Penatgon's decision to disconnect the "mail bridges" that connect the two networks and the fact that Pentagon officials did not announce its decision to system users.

"It's a hassle," said Stoll. "I suspect it's an overreaction...I hope the people at the Pentagon come to their senses soon."

System managers at the Mitre Corporation, a defense contractor in Bedford, Mass., discovered Monday that a hacker had breached the security of one of their computers as early as November 3. Although the company found no evidence that the intruder had stolen sensitive data or had broken into any other military computers, the Pentagon responded by severing communication channels between Arpanet and Milnet.

"It was a precautionary measure to provide a barrier to protect the users of the Milnet--to make sure that no information would be jeopardized," said the Pentagon spokesperson.

Computer system managers first noticed the disconnection when attempts to send mail to Milnet failed. When managers asked why mail was not flowing between the networks, the Pentagon told them it was a technical problem, according to The New York Times.

Stoll said he called friends on Tuesday and learned about the intruder--the real reason for the Pentagon's actions--then posted bulletins on Arpanet notifying the computer community.