SEOUL, Nov 20 (Reuters) - North Korea on Monday denounced the United States' potential sale of missiles to Japan and South Korea, calling it a dangerous act that raises tension in the region and brings a new arms race, state media reported.

In a statement carried by the KCNA news agency, the North's defence ministry said Pyongyang will step up measures to establish deterrence and respond to instability in the region, which it said was caused by the United States and its allies.

Japan plans to buy 400 Tomahawk missiles from the United States, part of its biggest military build-up since World War Two. The Pentagon said on Friday the U.S. State Department has approved the potential sale in a deal valued at $2.35 billion.

The United States has also recently announced the approval of a possible sale of Sidewinder missiles and Standard Missile 6 Block Is to South Korea.

"We warn that the more the United States profits from indiscriminate arms sales, the more it would have to pay for the security crisis," North Korea's statement said.

The statement comes as North Korea is preparing to launch a spy satellite. South Korean Defence Minister Shin Won-sik said on Sunday the launch could take place as early as this week.

"We sternly warn North Korea to squarely face the reality of the international community seriously condemning its illicit activities in one voice, and immediately suspend the plan to launch a military spy satellite now under preparation," South Korea's Joint Chiefs of Staff said in a statement.

The South Korean military said the satellite launch would be a provocation and a violation of U.N. Security Council resolutions that ban the North's use of ballistic missile technology.

Pyongyang has said it would demonstrate "more offensive and overwhelming counteraction capabilities," citing what it called "military threats" from the United States and its allies.

North Korea said on Wednesday it had successfully conducted static tests of "new-type high-thrust solid-fuel engines" for intermediate-range ballistic missiles (IRBMs), raising speculation over another missile test.

South Korea's National Security Council convened a meeting on Monday and said it would bolter the military's readiness to immediately respond to "any provocation" by the North.

Photo from AFP