Foreign Minister Yun Byung-se on Monday discussed Seoul-Washington relations and North Korea's nuclear weapon issue with Wendy Sherman, a former U.S.under secretary of state for political affairs who advises presidential candidate Hillary Clinton on diplomatic affairs, the foreign ministry said.

During the 30-minute talks held at the Ministry of Foreign affairs in Seoul earlier in the day, Yun stressed the importance of close cooperation between the allies in reining in North Korea's nuclear weapons program especially in light of heightened tension on the Korean Peninsula, the ministry said in a statement. 

The minister pointed to the joint talks of South Korean and U.S. foreign and defense ministers set for later in the month in the U.S., asking for Sherman's support on a stronger bilateral alliance, according to the statement. 

Sherman said the North Korean nuclear issue is becoming a very serious challenge, pledging her active role in further cementing the alliance in the next U.S. administration. 

She and Yun also shared the understanding that more sanctions and pressure are needed to resolve the North Korean nuclear issue.

The allies should jointly consider deploying all possible tools against North Korea, the statement quoted Sherman as saying.  

"North Korea's fifth nuclear test (on Sept. 9) made the seriousness of and urgency of countermeasures against the North Korean nuclear issue all the more evident," Yun said, highlighting an "extraordinary" approach needed over the matter.

Yun cited pressure over North Korea's human rights issues, the regime's labor export and disseminating outside information into the North as possible elements of the new approach.

The ministry said the latest talks was an opportunity for South Korea to confirm once again the U.S. diplomatic circle's support for the punitive approach over the nuclear issue.

Having served at the lead negotiator for the U.S.' deal to freeze Iran's nuclear program, Sherman is widely expected to take a key post if Clinton wins the presidential election. 

Sherman is visiting Seoul to attend the annual World Knowledge

Forum which kicks off on Tuesday for a three-day run in Seoul.  (Yonhap)