North Korea's late-night missile test has forced the South's pro-rapprochement President, Mr Moon Jae In, to harden his stance by ordering additional launchers to be deployed for a controversial American anti-missile shield.
South Korea and the United States have boosted military deterrence against the North, and Seoul is seeking to develop a more powerful missile.
Mr Moon, in a national security meeting held an hour after the intercontinental ballistic missile (ICBM) launch was detected late on Friday, called for the deployment of stalled launchers of the Terminal High Altitude Area Defence (Thaad) system.
Only two of six launchers have been installed even though the US wants Thaad to be operational as soon as possible. The delayed deployment, pending an environmental review, was meant to appease China, which opposes Thaad.
The situation puts Mr Moon in a dilemma, with analysts saying his credibility is at stake if he keeps using Thaad as a bargaining chip.
Dr Bong Young Shik of Yonsei University's Institute for North Korean Studies said Mr Moon's decision to deploy the rest of the launchers while insisting on an environmental review is self-contradictory.
It would appear "opportunistic and inconsistent" to the US, and "extremely ambiguous and contradictory" to China, said Dr Bong.
While the US did not comment, China was quick to protest yesterday, saying the deployment would only complicate matters and damage the strategic balance of the region without resolving security issues on the Korean peninsula.
Key events since North Korea's ICBM test
July 4: North Korea tests an intercontinental ballistic missile (ICBM) for the first time. Experts say the missile, which lands in Japan's Exclusive Economic Zone, is capable of reaching Alaska. Washington calls for global action. A day later, United States President Donald Trump lashes out at Beijing, arguing that US reliance on China to rein in Pyongyang is misplaced because of China's strong trade with North Korea.
July 8: US bombers carry out rare live fire drill in South Korea, flying close to the Demilitarised Zone in a show of force. A day later, North Korea hits out against the US-South Korea drills, accusing Washington of pushing the peninsula to the "tipping point" of nuclear war.
July 14: North Korea warns it will take "corresponding measures" if the United Nations adopts another sanctions resolution over the test.
July 17: South Korea proposes military talks with the North and a halt to hostile activities near the Korean border, which the North rejects with silence.
July 27: North Korea celebrates "Victory Day", which marks the anniversary of the end of the 1950-53 Korean War.
July 28: North Korea tests its second ICBM within a month in an unusual late-night launch. Pyongyang claims the missile, which landed in the waters off the Korean peninsula's east coast, proves its ability to strike the US mainland.
SOURCES: REUTERS, AGENCE FRANCE-PRESSE, BLOOMBERG
Since his election in early May, the left-leaning Mr Moon has been pushing to improve ties with the North, adopting a dual-track policy of engagement with pressure.
He outlined a vision for inter-Korean peace in a key speech in Berlin earlier this month as well as proposed military talks and sports collaborations with the North.
But Pyongyang has so far refused to budge, insisting that sanctions must be lifted first before dialogue can proceed. The regime has now test-fired two ICBMs this month, determined to demonstrate it is capable of striking the US.
Dr Bong said the Moon administration's response to Friday's test shows that there is not much South Korea can do independently to influence the North's behaviour. "All that talk about the Berlin vision and South Korea obtaining international endorsement to be in the driver's seat sounds very empty."
Dr Lee Seong Hyon from the Sejong Institute think-tank said Mr Moon has "very limited political manoeuvring room", and will face pressure from both the US and domestic circles to be tougher on the North, and to fully deploy Thaad, which would upset China.
"Mr Moon will also have a hard time maintaining his policy of engagement with North Korea. His challenge is coming from all sides. It's not (North Korean leader) Kim Jong Un, but Mr Moon who is being cornered."