MUNICH, Germany (AFP) - The United States on Saturday slammed an offer by North Korea to suspend future nuclear tests temporarily if Washington cancels military drills with the South as an "implicit threat."

Pyongyang was "inappropriately" linking routine military exercises between Washington and Seoul to the possibility of a nuclear test, State Department spokeswoman Jen Psaki said.

"A new nuclear test would be a clear violation of North Korea's obligations under multiple UN Security Council resolutions," Ms Psaki told reporters travelling with US Secretary of State John Kerry to India during a stopover in Munich.

North Korea's proposal was passed to the US side through a "relevant channel" on Friday, the North's official KCNA news agency said Saturday.

The message called on Washington to help ease tensions on the Korean peninsula by suspending all of this year's joint military exercises in South Korea "and its vicinity".

But Ms Psaki said the North's statement "inappropriately links routine US-ROK (South Korea) exercises to the possibility of a nuclear test by North Korea is an implicit threat".

She stressed that Washington "remains open to dialogue with" the North, but talks had to be aimed at "returning to credible and authentic negotiations on the denuclearisation of the Korean Peninsula".

"We call on the DPRK (North) to immediately cease all threats, reduce tensions, and take the necessary steps toward denuclearisation needed to resume credible negotiations," she added.

The United States, which has close to 30,000 troops permanently stationed in South Korea, conducts a series of joint military exercises with its key Asian ally every year.

Ms Psaki said the exercises were "transparent, defence-oriented, and have been carried out regularly and openly for roughly 40 years".