South Korea's foreign and defense ministers arrived in Washington on Tuesday for security and alliance talks with their US counterparts that are expected to focus on how to counter ever-growing nuclear and missile threats from North Korea.

Foreign Minister Yun Byung-se and Defense Minister Han Min-koo will join US Secretary of State John Kerry and Defense Secretary Ash Carter in Wednesday's "two plus two" talks, a biennial gathering designed mainly to demonstrate the firmness of the alliance and discuss strategies to deal with the North.

The meeting comes just a few days after the communist nation carried out a banned test Saturday of a Musudan intermediate-range ballistic missile, believed to be capable of reaching the US territory of Guam, about a month after its fifth nuclear test.

The test was unsuccessful as the missile exploded shortly after take-off, but the launch still showed how committed the North is to developing nuclear-armed, long-range missiles. Officials and experts have warned Pyongyang could keep conducting nuclear and missile tests in coming months.

Wednesday's talks are expected to focus on ways to strengthen the US "extended deterrence" protection of South Korea and to ramp up pressure and sanctions on Pyongyang, including through a strong new U.N. Security Council sanctions resolution and unilateral sanctions of their own.

"Extended deterrence" refers to the threat of nuclear retaliation to deter attacks on allies. The US has provided extended deterrence or a "nuclear umbrella" to South Korea after withdrawing nuclear warheads from the country in the early 1990s.

"We will discuss comprehensive strategies to deal with North Korean threats. In particular, we're going to have in-depth discussions on ways to specify and institutionalize extended deterrence, which is a key element in the US security commitment to South Korea," Yun told reporters during a joint visit with Han to the Korean War Veterans Memorial in Washington.

Yun also said the two sides will discuss ways to maximize effects of sanctions on the North.

On Thursday, the two sides are scheduled to hold annual defense ministers talks, known as the Security Consultative Meeting (SCM), where Han and Carter are expected to discuss detailed "extended deterrence" measures, possibly including permanently deploying US "strategic assets" in the South, such as nuclear-capable B-52 and B-1B bombers, F-22 stealth fighter jets and nuclear-powered submarines.

"In the SCM talks, we will jointly assess North Korea's threats and the situation in the North ... and discuss ways to guarantee the implementation of extended deterrence, including the US nuclear umbrella, so as to cope with North Korea's nuclear and missile threats," Han told reporters during the visit to the war memorial.

The US has temporarily sent such strategic assets to South Korea as a show of force in the wake of the North's two nuclear tests in January and September, but perceptions have grown among South Koreans that such one-off missions are not enough at a time of unprecedented threats from the North.

Permanent deployment of such military hardware is expected to reassure South Koreans of the US defense commitment amid heightened security jitters that sparked calls for developing the country's own nuclear weapons or bringing US nuclear bombs back into the country.

Such sophisticated weapons would also serve as a strong warning against the North.

In the SCM talks, the two sides are also expected to check on progress in efforts to deploy the US THAAD missile defense system in the South, while reaffirming that the deployment is aimed only at defending against North Korean threats and poses no threats to China and other countries. (Yonhap)