US, South Korea begin major navy drill
Tensions over the North's weapons programmes have soared in recent months, with Pyongyang carrying out a series of missile launches and its sixth nuclear test, its most powerful yet, in defiance of multiple sets of UN sanctions.
The United States has since ramped up military drills with South Korea and Japan, its two closest allies in the region.
"The latest exercise is aimed at maintaining readiness against North Korea's naval provocation and improving capabilities to carry out joint operations," a South Korean navy spokesman told reporters.
The 10-day drills are taking place on the southern side of the de facto maritime border known as the Northern Limit Line, the spokesman added.
Pyongyang habitually condemns such joint exercises and the state-run KCNA news agency on Saturday called the Ronald Reagan's participation a "reckless act of war maniacs as it only drives the tense situation on the peninsula into the point of explosion".
The exercises are the latest instance of US military hardware movements around the Korean peninsula.
On Friday the nuclear-powered submarine USS Michigan arrived in the southern port of Busan, according to Yonhap news agency, days after another nuclear-powered submarine -- the USS Tucson -- left.
The US is showcasing a line-up of its warplanes including the B-1B bomber, and F-22 and F-35 stealth fighters at the Seoul International Aerospace and Defense Exhibition which opens Tuesday.
Organisers said the event was a showcase for South Korean arms exporters, rather than a platform for foreign manufacturers as in the past, but added that the display of Seoul and Washington's newest military assets would send a strong message about the allies' readiness.
US Forces Korea said Sunday they would later this month conduct the annual Courageous Channel training, to prepare US service members and their families for evacuation during a natural or man-made disaster on the peninsula.
"Although not directly tied to current geopolitical events, our forces must be ready in all areas," USFK commander General Vincent Brooks said in a statement.
President Donald Trump has engaged in an escalating war of words with North Korean leader Kim Jong-Un, trading personal insults and threats of miltary strikes and raising concerns about an outbreak of hostilities.
"He's not seeking to go to war," Tillerson said on CNN's State of the Union.
The North's missile and nuclear capabilities have made significant progress under Kim, who told party officials this month that the country's atomic weapons were a "treasured sword" to protect it from aggression.