South Korea's pro-United States diplomacy and the intensifying containment and provocation against the Democratic People's Republic of Korea by the two countries have sparked mounting concerns over regional stability, said senior Korean experts on Monday. South Korea and the U.S. have issued the Washington Declaration, which announced the establishment of a new Nuclear Consultative Group and the upcoming visit of a U.S. nuclear ballistic missile submarine to South Korea for the purpose of strengthening the so-called "extended deterrence."