Russia and China have agreed to take countermeasures over deployment of a U.S. anti-ballistic missile system in the Korean Peninsula, China’s state-run Xinhua news agency reported Thursday. The deployment of the Terminal High Altitude Area Defense (THAAD) system in South Korea to tackle growing nuclear threat from North Korea has left Beijing and Moscow concerned over security in the region.

The countermeasures will be taken to protect China and Russia’s interests and to maintain strategic balance in the region, Xinhua reported, citing a statement released by both the nations. Moscow and Beijing also urged the U.S. and South Korea to avoid deploying THAAD.

South Korea, which has substantial trade relations with China, had previously denied any formal discussion with the U.S. about the installation of THAAD, which can reportedly shoot down short-, medium- and immediate-range ballistic missiles. However, it decided otherwise after series of missile and nuclear tests by carried out by North Korea last year. In July, Seoul and Washington announced they had agreed to install THAAD in South Korea.

China and Russia have maintained its opposition to THAAD, citing security concerns. Beijing has consistently said that the THAAD system could be used to monitor its missile launches as far inland as Xian in the northwest.

Moscow, meanwhile, argues that the deployment could aggravate tensions in the Korean Peninsula. Last July, Russia urged South Korea and the U.S. to “weigh all circumstances and prevent any unreasoned actions which may lead to tragic and irreversible consequences for the situation both in North East Asia and beyond.”

However, in an interview to Russian news agency Sputnik last September, the then South Korean President Park Geun-hye maintained THAAD will not be used against Russia or other countries.

“There is no reason, nor practical benefit, for the THAAD system to target any third country, and the Korean Government does not have any such intentions or plans,” Park said at the time. “So far, the Korean Government has faithfully explained our basic position to the Russian Government. If Moscow feels that there is a need for additional explanation, the Korean Government will continue to communicate closely in the days to come.”

South Korea is planning to deploy the anti-ballistic missile defense system by the end of this year.