(Reuters) - North Korea said on Saturday it was willing to suspend nuclear tests if the United States agreed to call off annual military drills held jointly with South Korea, saying the exercises were the main reason for tension on the Korean peninsula.

The proposal, which the North's official KCNA news agency said was conveyed to Washington on Friday through “a relevant channel,” follows an often-repeated demand by Pyongyang for an end to the large-scale defensive drills by the allies.

"The message proposed (that) the U.S. contribute to easing tension on the Korean peninsula by temporarily suspending joint military exercises in South Korea and its vicinity this year," KCNA said in a report.

"(The message) said that in this case the DPRK is ready to take such a responsive step as temporarily suspending the nuclear test over which the U.S. is concerned," KCNA said, using the short form for the Democratic People's Republic of Korea.

North Korea has conducted three nuclear tests, the last in February 2013, and is under layers of U.N. sanctions for defying international warnings not to set off atomic devices in pursuit of a nuclear arsenal, which Pyongyang calls its “sacred sword.”

It often promises to call off nuclear and missile tests in return for comparable steps by Washington to ease tensions. It reached such a deal in February 2012 with the United States for an arms tests moratorium only to scrap it two months later.

The United States and South Korea have stressed that the annual drills, which in some years involved U.S. aircraft carriers, are purely defensive in nature, aimed at testing the allies' readiness to confront any North Korean aggression.

Tension peaked on the Korean peninsula in March 2013 when the North ratcheted up rhetoric during the annual drills, with Pyongyang threatening war and putting its forces in a state of combat-readiness.