The Chilean government's failure to punish soldiers responsible for the fatal burning of a teen-aged Washington resident in Santiago last year demonstrates that Chile's security forces are able to commit human rights violations with relative impunity, the State Department charged yesterday.

A lengthy statement read by department spokeswoman Phyllis Oakley recalled the July 2, 1986, incident in which Rodrigo Rojas, a Chilean citizen who lived here, allegedly was doused with gasoline and set afire during antigovernment demonstrations. He died of burns five days later.

A companion, Carmen Gloria Quintana, is still recovering from burns over 60 percent of her body.

An Army officer has been charged with failing to provide adequate care for the two victims. But Oakley said:

"Regretfully, a year after the burnings,

we appear to be no closer to the conclusion

of an ongoing military court investigation

and clarification of responsibility for the crime.

"The glacial progress in the Rojas case is not unique," Oakley added, referring to Chile's rejection of a U.S. request that President Augusto Pinochet's government arrest and expel two senior Chilean intelligence officers wanted here in the 1976 car-bomb murder of former Chilean ambassador Orlando Letelier.

"The Chilean government, while rejecting our request to expel them for trial in the United States, has so far failed to ensure any meaningful prosecution of these two former officials," she said.

"It continues to be the pattern in Chile that opponents of the government are vigorously prosecuted, but that official investigation into abuses of authority by security forces rarely bring results," Oakley concluded.