The United States has placed a destroyer off the South Korean coast to defend against a possible missile strike, the latest in a series of publicized American deployments to counter North Korean threats.
The USS Fitzgerald was moved to the southwestern coast after taking part in annual military exercises, instead of returning to its home port in Japan, an American defense official told AFP on condition of anonymity.
The deployment came hours after a gathering of North Korea's rubber-stamp parliament adopted a law formalizing the country's status as a nuclear weapons state.
The Korean peninsula has been caught in a cycle of escalating tensions since the North launched a long-range rocket in December and followed it with a nuclear test in February.
Subsequent UN sanctions and annual South Korea-US military exercises have been used by Pyongyang to justify a wave of increasingly dire threats against Seoul and Washington, including warnings of missile strikes and nuclear war.
In this light, the shifting of the USS Fitzgerald was "a prudent move", the defense official said, adding that it would offer "greater missile defense options should that become necessary".
Earlier on Monday, the United States military announced it had deployed F-22 Raptor stealth fighters to South Korea as part of the ongoing annual "Foal Eagle" joint military exercise.
Pentagon spokesman George Little said the F-22s were an "important display" of America’s commitment to its military alliance with the South.
"The North Koreans have a choice. They can continue to engage in provocations, with bellicose, overheated, irresponsible rhetoric, or they can choose the path of peace," Little told reporters, according to AFP.
North Korea has already threatened to strike the US mainland and US bases in the Pacific in response to the participation of nuclear-capable US B-52 and B-2 stealth bombers in the "Foal Eagle" drill.
But the tough talk has yet to be matched by action on the ground, according to American intelligence.
"Despite the harsh rhetoric we're hearing from Pyongyang, we are not seeing changes to the North Korean military posture, such as large-scale mobilizations and positioning of forces," White House spokesman Jay Carney said.
Meanwhile, South Korea's new president, Park Geun-Hye, told senior military officials that any provocation from the North should be met with a "strong and immediate" military response, no matter what the political fallout.
The assertive US and South Korean stances suggest the two allies are working in close concert, and South Korean Foreign Minister Yun Byung-Se was in Washington for talks Tuesday with new US Secretary of State John Kerry.
The "continuing military threats from the North" will top the agenda, Yun's ministry said in a statement.
The high-stakes standoff on the Korean peninsula has triggered widespread international concern of an accidental conflict that could escalate rapidly.