Seoul and Washington are looking to build up their alliance towards what they are calling a "new frontier."
U.S. Deputy Secretary of State Tony Blinken sat down with South Korean foreign minister Yun Byung-se on Tuesday to go over the agenda for President Park Geun-hye's upcoming summit with President Barack Obama and to reinforce cooperation against a possible rocket launch by the North.
"With the latest threats coming from Pyongyang, we've reaffirmed our alliance and readiness which is stronger than ever.
We realize the importance of preventive diplomacy to reign in North Korea from taking such action. But if it carries out a provocation, we'll jointly counter the situation in a very stern and firm manner."
Citing Iran as an example of how the U.S. is willing to negotiate Blinken encouraged Pyongyang to give up its nuclear ambitions and to return to the six-party talks.
"We are united, with the United States and South Korea, but also I believe with Japan - I had conversation with Russia, China and all agree strongly that not only should North Korea not take the step, but it must return to meaningful efforts to denuclearization."
But Pyongyang may not be so close to compromising its nuclear ambitions.
Visiting Seoul for talks with foreign minister Yun Byung-se IAEA chief Yukiya Amano told reporters that the agency detected suspect activities at North Korean nuclear facilities.
"(Yes,) we have observed activities at Yongbyon that coincide with North Korea’s declaration to expand their activities. We have observed the discharge of waters or transportation of equipment to the facility and some indications of operations of the 5-mega-watt reactor. But we do not have inspectors on the ground. (So) we cannot say for sure."
Amano added that not being able to have IAEA inspectors on the ground in the North is a major concern for the nuclear watchdog as tries to verify any possible activities.
Song Ji-sun, Arirang News.