WASHINGTON, Dec 4 (Reuters) - Phone companies are

denying the U.S. military's requests for data about

vulnerabilities in the American telecom system, according to a

letter released Wednesday.

In answers provided to Democratic Senator Ron Wyden, the

Pentagon said it had requested the results of digital security

tests and audits from the carriers it contracts with for

telecommunications services but was turned down on the grounds

that "they are considered attorney-client privileged

information."

In a letter co-signed with Republican Senator Eric Schmitt,

Wyden said that the answer wasn't acceptable.

While the Pentagon was among the largest buyers of wireless

telephone service in the United States, "it has failed to use

its purchasing power to require cyber defenses and

accountability from wireless carriers," the letter said.

The carriers weren't identified by name in the military's

responses, but AT&T ( T ), Verizon, and T-Mobile

are among those that provide commercial wireless service for

unclassified use, according to the letter.

AT&T ( T ), Verizon, and T-Mobile didn't immediately return

messages seeking comment. The Pentagon didn't immediately return

an email.

The security of American telecommunications - particular

over commercial carriers - has come into focus following a

series of dramatic intrusions blamed on Chinese hackers.

U.S. officials have previously alleged that a group of

hackers dubbed "Salt Typhoon" stole limited telephone audio

intercepts, along with a larger tranche of call record data.

Officials have said those records mainly concerned people in the

Washington area.

Later Thursday senators are due to receive a classified

briefing on Salt Typhoon and its impact on U.S. data.

Chinese officials have previously described the allegations

as disinformation and that Beijing "firmly opposes and combats

cyber attacks and cyber theft in all forms."