New US Deputy Secretary of State Antony Blinken held talks in Seoul Monday on nuclear-armed North Korea, which foreshadowed his trip to the rival South with a series of missile tests.

Blinken sat down with his South Korean counterpart Cho Tae-Yong at the start of an Asian tour that will also take him to China and Japan.

North Korea and its nuclear weapons programme were set to dominate the Seoul leg of the trip, which saw the North test-fire five short-range missiles into the sea as Blinken arrived on Sunday.

The day before, Pyongyang trumpeted the test-firing of a new "ultra-precision" anti-ship cruise missile under the watchful eye of leader Kim Jong-Un.

North Korea often test-fires missiles and rockets to coincide with high-profile visits to the rival South, and at times of military tension on the divided peninsula.

Blinken's visit comes weeks before the launch of annual joint US-South Korea military exercises that regularly see North-South relations go into a vertiginous tail-spin.

Pyongyang views the drills as provocative rehearsals for invasion, while Seoul and Washington insist they are defensive in nature.

Last month, North Korea had offered to suspend any further nuclear test if this year's joint exercises were cancelled -- a proposal the US State Department described as a "non-starter."

"It's a non-starter because North Korea doesn't have the right to bargain, to trade, or to ask for a payoff in return for abiding by international law," Assistant Secretary of State Daniel Russel told a press briefing in Washington ahead of Blinken's visit.

"That's not how it works," Russel said, reiterating Washington's stance that it will only consider negotiating with Pyongyang when it shows a tangible commitment towards denuclearisation.

North Korea has conducted three nuclear tests -- most recently in February 2013 -- and its moratorium offer was seen in Washington as an "implicit threat" to carry out a fourth.

Last week, the North's top military body ruled out resuming dialogue with the "gangster-like" United States, and vowed to respond to any US aggression with nuclear strikes and cyber warfare.

While noting Pyongyang's "seemingly inexhaustible supply of hyperbolic rhetoric," Russel said North Korea's potential for provocation was such that any threat had to be taken seriously.

Tensions escalated last month as President Barack Obama imposed fresh sanctions on North Korea following a damaging cyber attack on Hollywood studio Sony Pictures that Washington blamed on Pyongyang. (AFP)