U.S. Secretary of Defense Lloyd Austin arrived in South Korea on Monday. 

An E-4B Nightwatch plane, carrying Austin, landed at Osan Air Base in Pyeongtaek, south of Seoul, at 4:30 p.m. 

The defense chief was greeted by U.S. Forces Korea Commander Gen. Paul LaCamera and other U.S. military officials, before he departed the base at 4:50 p.m. via a helicopter.

In a post on Twitter, Austin said that he looks forward to meeting his South Korean counterpart and other senior government officials to chart an ambitious path forward and advance their shared security priorities in the Indo-Pacific. 

Austin also said in a contribution piece sent to the Yonhap News Agency that if an adversary challenges either South Korea or the U.S., it would be like challenging the alliance as a whole. 

The U.S. defense chief is scheduled to meet with South Korean defense minister Lee Jong-sup on Tuesday to discuss ways to strengthen the U.S. extended deterrence. 

The talks are expected to focus on ways to improve the readiness of the U.S. extended deterrence, including the discussion-based table-top exercise that the allies are planning to hold in the U.S. next month, under the scenario of North Korea's use of nuclear weapons.

The U.S. defense secretary is also reportedly scheduled to meet with President Yoon Suk Yeol during this trip.