Following the agreement between Kim and Putin, the US will send a carrier battle group

A nuclear-powered U.S. aircraft carrier arrived in South Korea on Saturday. The exercise is aimed at increasing military preparation for the threat from North Korea, which has escalated following the announcement of a security pact with Russia. The arrival of the USS Theodore Roosevelt battle group in Busan came a day after South Korea summoned the Russian ambassador to protest the deal between Russian President Vladimir Putin and North Korean leader Kim Jong Un. The exercise is scheduled to begin later this month, according to AP.

US Rear Admiral Christopher Alexander, commander of Carrier Strike Group Nine, said the exercise was designed to sharpen the ships’ tactical capabilities and improve interoperability between the two countries’ navies “to ensure we are ready to respond to any crisis or emergency.” The South Korean navy said in a statement that the carrier’s arrival demonstrated the “vigorous readiness of allies to respond to advancing North Korean threats.” The visit came seven months after another aircraft carrier, the USS Carl Vinson, arrived in South Korea in a show of force toward the North.

The Roosevelt strike group also took part in a three-way exercise with South Korean and Japanese naval forces in the disputed East China Sea in April, where concerns about China’s territorial claims are growing, according to AP. Faced with the growing threat from North Korea, the U.S., South Korea and Japan have expanded their joint exercises and increased the visibility of strategic U.S. military assets in the region. The U.S. and South Korea have also updated their nuclear deterrence strategies, with Seoul seeking stronger assurances that Washington would use its nuclear capabilities quickly and decisively to protect its ally from a North Korean nuclear attack. (More U.S. military reports.)