Dygalo said the United States was flying an unmanned rescue vehicle from a naval base in San Diego to the site where the Russian mini-submarine sank to the bottom after apparently becoming entangled in a fishing net at a depth of 190 meters.
Dygalo said the clock was running out for the crew of seven.
"Unfortunately the real situation now is that there is enough air only for 24 hours. The rescue operation will continue around the clock, without any breaks or interruptions," Dygalo said.
Dygalo said Britain was providing "rescue means" for the operation but he did not elaborate on those means.
Russia has asked for assistance from Japan, which has dispatched several rescue craft. But Tokyo said earlier the boats would not reach the area until early on 8 August.