Americans are getting a bit less sodium in their diets, but most processed foods still have a relatively high amount of salt, the private Center for Science in the Public Interest reports.

"This year, for the first time, considerably more foods have gone down in sodium content than have gone up," reported Bonnie Liebman, nutrition director for the public interest group.

But, she added, "the sodium content of the overwhelming majority of processed foods remains high. If the current trend continues, substantial reductions in the sodium content of the overall food supply will be decades away."

The center has been collecting information on the sodium content of foods since 1983 and issuing its annual "Sodium Index" reports on its findings. Sodium, primarily found in table salt, is of concern because many medical authorities believe it contributes to high blood pressure and other medical problems.

An average of 100 common processed foods averaged 595 milligrams of sodium last year, the new report said. That was down from 609 milligrams in 1985. The index for 1984 was 621 milligrams and in 1983 it was 624.

An extended index of 2,500 foods grouped into 165 product lines, found that 78 percent of the items had no change in sodium content, 15 percent showed declines and 7 percent reported increases, the center said.