A group of South Korean students broke into the residence of American ambassador Harry Harris on Friday, in a protest against Donald Trump’s campaign to get the Asian nation to pay more for US military support.

Nineteen students, who described themselves as members of a liberal university students’ group, were detained by police after staging a protest against plans to impose a bigger financial burden for the stationing of US troops in the country, the Yonhap News Agency reported.

The students used a ladder to climb the walls of the ambassador’s residence, part of an old South Korean palace, and urged Harris to leave the country.

The incident happened days before officials from the US and South Korea are due to meet in Honolulu for the next round of talks on sharing defense costs.

After the incident, Seoul police dispatched 80 more officers to beef up security of the envoy’s home, according to Yonhap.

Earlier this year, the two allies reached a one-year cost-sharing deal for maintaining about 28,500 American troops in South Korea. That deal expires at the end of 2019.

The relationship between the two allies soured after Seoul abruptly announced the termination of a three-year-old pact with Japan – another US key ally – for exchanging classified military information. That was in response to Japan’s move to restrict exports of key materials for the manufacture of semiconductors to South Korea.