South Korea's rejection of China's pressure over its decision to host the US THAAD missile defense system represents a "new degree of strategic trust" with Washington, a congressional report showed Friday.

The Congressional Research Service made the assessment in the latest report on US-South Korea relations, saying that North Korea's provocations appear to have driven the military alliance between Seoul and Washington closer.

Seoul's decision to host a Terminal High Altitude Area Defense battery not only acknowledged North Korea's growing nuclear and missile capabilities but also "indicated South Korea's willingness to rebuff China," the report said.

In July, Seoul and Washington jointly announced the decision to deploy THAAD to better defend against the North's growing nuclear and missile threats. China has strongly protested, claiming THAAD, especially its powerful X-band radar, hurts its security interests.

"China went further, threatening retaliatory moves, such as reducing tourism and denying visas, moves that could further alienate the South Korean public," the CRS report said.

South Korean President Park Geun-hye had cultivated a stronger strategic relationship with China in order to influence Beijing's North Korea policy, but as China fails to curb Pyongyang's provocations, Seoul appeared to tilt toward US wishes in joining its missile defense system, the report said.

"Seoul's willingness to withstand Beijing's harsh response may represent a new degree of strategic trust with the United States," it said.

The North's provocations also helped forge closer trilateral cooperation between the US, South Korea and Japan, leading the three countries to conduct joint maritime exercises focused on tracking potential North Korean missile launches, the report said.

The three countries have also launched a coordinated global campaign to "persuade other countries to curtail relations with North Korea, particularly those such as the North's state-run labor export programs that are believed to generate income for the government in Pyongyang," it said.

The report also took note of growing support in South Korea for nuclear armament.

It cited a survey this year by the Asan Institute as showing 65 percent of the respondents supporting nuclear weapons development while only 31 percent expressed opposition.

"This is the highest level of support since the Asan Institute began asking this question in 2010. Debates about nuclearization have become more prominent in political circles in Seoul following the 2016 tests," it said, referring to the North's January and September nuclear tests.

The report noted that a group of ruling party lawmakers called on the government to consider developing nuclear weapons and that the National Unification Advisory Council, a presidential advisory group, also recommended in an October report that South Korea consider a return of US tactical nuclear weapons to the country.

"US policymakers have reiterated their 'ironclad commitment' to defend South Korea and flew two B-1B long-range nuclear-capable bombers over the Korean Peninsula as a show of force and reassurance following the 2016 nuclear tests," the report said.

"However, some South Koreans have pointed to the failure of the United States and others to stanch Pyongyang's growing nuclear capability as justification for Seoul to pursue its own nuclear arsenal," it said.

The South, however, could face negative consequences if it seeks nuclear development, such as reduced international standing in the campaign to denuclearize North Korea, the possible imposition of economic sanctions and potentially encouraging Japan to develop nuclear weapons capability, the report said.

"For the United States, South Korea developing nuclear weapons could mean diminished US influence in Asia, the unraveling of the US alliance system and the possibility of creating a destabilizing nuclear arms race in Asia," it said. (Yonhap)