The US is worried that it’s submarine fleet is falling behind China and Russia’s as both countries aggressively push to expand and modernize their navies.

Admiral Harry Harris told the House Armed Services Committee on Wednesday that US Pacific Command “suffers shortage of submarines today, my requirements are not being met.”

And, according to Foreign Policy, Harris told the committee that his main concern was that the Pentagon was not managing to keep pace with its rivals in the region.

Harris directly linked this threat to the rising submarine powers of Russia and China.