The White House has dismissed as "absurd" an accusation by North Korea that US President Donald Trump had declared war on the Asian nation.
North Korean Foreign Minister Ri Yong Ho claimed on Monday that Pyongyang could now shoot down US aircraft.
"Since the US declared war on our country, we will have every right to [take] countermeasures, including the right to shoot down the US bombers even when they are not yet inside the airspace border of our country," Ri told reporters in New York, where he was attending the UN General Assembly.
White House spokeswoman Sarah Sarah Sanders dismissed the claim.
"We have not declared war on North Korea and frankly the assertion of that is absurd," Sanders said.
She added, "It's never appropriate for a country to shoot down another country's aircraft over international airspace."
The Pentagon said the US military was prepared to defend the US and its allies and would present options to the president should he decide to respond militarily.
The US and North Korea have been engaged in a heated exchange in the face of recent missile and nuclear tests by North Korea, and the US on Friday had expanded its sanctions regime against Pyongyang in a bid to cut off international banking and trade.
US Air Force bombers and fighter jets had also flown over international waters off the east coast of North Korea on Saturday in a "demonstration of US resolve" in the face of Pyongyang's provocations.
Trump over the weekend dismissed Ri's speech at the United Nations, declaring: "If he echoes thoughts of Little Rocket Man, they won't be around much longer!"
Ri had told the General Assembly that Trump's remarks were making a North Korean "rocket's visit to the entire US mainland inevitable all the more".
On Monday, Ri responded to Trump's remarks, declaring: "Last weekend, Trump claimed that our leadership wouldn't be around much longer and he declared a war on our country. Even the fact that this comes from someone who is currently holding the seat of the US presidency is clearly a declaration of war."
Meanwhile in letters sent over the weekend, North Korea condemned Trump's administration and the actions of "US imperalists", urging foreign parliaments and political parties to take a stand, state media reported on Monday.
A letter to foreign parliaments from the Foreign Affairs Committee of the Supreme People's Assembly of the Democratic People's Republic of Korea "bitterly condemned the reckless remarks of Trump as an intolerable insult to the Korean people, a declaration of war against the DPRK and grave threats to the global peace", North Korean state news agency KCNA reported.
"If Trump thinks that he would bring the DPRK, a nuclear power, to its knees through nuclear war threat, it is a big miscalculation and ignorance," KCNA said.