President Donald Trump said Tuesday the United States is "totally prepared" to take military action against North Korea if necessary to curtail the country's nuclear weapons development.

"We are totally prepared for the second option, not a preferred option," Trump told reporters at the White House. "But if we take that option, it will be devastating...for North Korea. That's called the military option."

"If we have to take it, we will," he said, in response to North Korean Foreign Minister Ri Yong Ho's assertion on Monday that Pyongyang has the right to shoot down U.S. strategic bombers even when they are not flying in North Korean airspace.

Trump said his remarks were a "reply" to the North's threat, not an "original statement" from the U.S. side.

During a visit to New York for the U.N. General Assembly, Ri also said Washington has declared war against Pyongyang, a claim the White House denied.

Trump said North Korean leader Kim Jong Un is acting "very badly," and that he is saying "things that should never ever be said."

As part of efforts to step up pressure on North Korea, the U.S. Treasury Department said Tuesday it has sanctioned eight North Korean banks and 26 individuals over their ties to Pyongyang's development of nuclear weapons and ballistic missiles.

The blacklisting was in line with a new executive order -- signed by Trump last week -- that allows the targeting of companies and entities that finance and facilitate trade with North Korea.

Apparently with Chinese banks in mind, U.S. officials say banks doing business with North Korea will not be allowed to operate in the United States.

According to the Treasury, the latest sanction hits 26 North Korean nationals working as representatives of North Korean banks in China, Russia, Libya and the United Arab Emirates.

"This further advances our strategy to fully isolate North Korea in order to achieve our broader objectives of a peaceful and denuclearized Korean Peninsula," Treasury Secretary Steven Mnuchin said.

"This action is also consistent with U.N. Security Council resolutions" that ban North Korea from engaging in nuclear and missile activities, Mnuchin said.

Speaking at a joint news conference with Spanish Prime Minister Mariano Rajoy after their White House meeting, Trump hailed China's latest action to restrict its trade with North Korea so as to compel it to change its provocative behavior.

"I applaud China for breaking off all banking relationships with North Korea, something that people would have thought unthinkable even two months ago," he said. "I want to thank President Xi" Jinping of China.

Trump also praised Spain for its recent decision to expel the North Korean ambassador from Madrid and for joining international efforts to isolate the Kim regime.

"It is time for all responsible nations to join forces, to isolate the North Korean menace," Trump said. "All nations must act now to ensure the regime's complete denuclearization."

U.S. officials have said Washington has yet to see a signal from North Korea that the country is ready to engage in serious negotiations on denuclearization and ceasing its provocative behavior.

Following the Sept. 3 test of what Pyongyang said was a hydrogen bomb that can be mounted on an intercontinental ballistic missile, Ri, the North's foreign minister, suggested last week in New York that Pyongyang could detonate a hydrogen bomb over the Pacific Ocean.

There is growing speculation that North Korea may conduct yet another provocative act around the founding anniversary of its ruling Workers' Party of Korea on Oct. 10.