SEOUL (Reuters) - South Korean President Park Geun-hye pledged on Tuesday further “strong” measures against North Korea, after suspending operations at a jointly run industrial park as punishment for the North’s recent long-range rocket launch and nuclear test.

South Korean President Park Geun-Hye speaks during a joint news conference with German President Joachim Gauck (unseen) after their meeting at the presidential house in Seoul, South Korea October 12, 2015. REUTERS/Jeon Heon-Kyun/Pool

It was time to face the “uncomfortable truth” that the North would not change, Park said in comments that mark a significant reversal for a leader whose policy on Pyongyang had been based on what she’d described as “trustpolitik” that she hoped would lay the ground for eventual unification.

Park said past efforts at engagement had not worked. “It has become clear that the existing approach and goodwill are not going to break the North Korean regime’s nuclear development drive,” she told parliament.

Washington and Seoul are seeking support from Beijing, Pyongyang’s main ally, for tougher sanctions against North Korea for the Feb. 7 rocket launch and January’s nuclear test.

“The premise of ‘trustpolitik’ was that the North was a partner. The president’s comments in effect mean that premise was wrong. It is a complete turnabout in North Korea policy,” said Hong Sung-gul, a political science professor at Kookmin University.

South Korea last week suspended the operation of the Kaesong industrial zone, which had been run jointly with the North for more than a decade. The industrial park was a key source of hard currency for the impoverished North.

Seoul also agreed to enter talks with Washington for deploying a missile defence system in South Korea, which China strongly opposes.

“The government will take strong and effective measures for the North to come to the bone-numbing realisation that nuclear development will not help its survival but rather it will only speed up the collapse of the regime,” Park said.

She did not specify what the measures would involve.

Seoul and Washington have said the rocket launch was in fact a long-range missile test that violated U.N. Security Council resolutions. The North said the launch was part of its scientific programme designed to launch satellites into space.

RETURN TO HARD LINE

Park, whose father ruled South Korea for 18 years, had set out an ambitious plan early in her single five-year term to prepare the two Koreas for unification. That, and her call for confidence-building steps between the rivals, were a departure from the hard-line policy of her predecessor, Lee Myung-bak.

In a 2014 speech in Germany that became known as the “Dresden declaration”, Park called for a new push for cooperation and exchange to bring the two societies closer. She hoped Germany’s reunification would eventually be emulated on the Korean peninsula.

Park had sought to engage the North in dialogue since then, while also responding firmly to moves by North Korea that raised tensions, including a landmine blast at the border last year that wounded two South Korean soldiers.

Her top national security officials met senior aides to the North’s young leader, Kim Jong Un, in August and agreed to take steps to improve ties in the most substantial diplomatic engagement since a 2007 summit between the Koreas.

Those efforts have since fizzled.

South Korea is now on heightened alert for any kind of “extreme actions” Pyongyang might take, Park said.

South Korea’s Defence Ministry has said upcoming annual joint military drills with U.S. forces would be the largest ever. Seoul has been in talks with Washington to deploy U.S. strategic assets on the Korean peninsula, such as stealth bombers and a nuclear-powered submarine.