Meanwhile, South Korean media showed six US Air Force F-22 Raptors, Washington's top-of-the-line stealth fighters, arriving in South Korea on Saturday to participate in the Vigilant Ace 18 air combat exercise, an annual US-South Korea drill the US Air Force says is created to boost the "combat effectiveness" of the alliance.
"If there's an underground nuclear test, then you need to get ready for a very serious response by the United States", Graham said.
McMaster said the possibility of war with the North was "increasing every day".
South Korea's military believes that the latest missile, which flew 950 kilometers before splashing down in waters near Japan, is potentially capable of striking targets as far as 13,000 kilometers, which would put Washington within reach. "However, the quake could have been caused by geological changes created from the recent nuclear explosion", said an agency official who asked not to be named. "It's something that places us at direct risk but places the world at risk".More news: Syrian state media: Israeli missiles strike near Damascus
Graham said he has had extensive discussions with the Trump administration about the situation.
The United States has demanded tougher global sanctions in response to the latest missile tests, including cuts in oil shipments to the isolated state.
United Nations Security Council ministers will meet on 15 December to discuss North Korea's nuclear and missiles programs and the body will also meet separately in December to discuss human rights abuses in the North Asian country, an annual meeting that its ally China has tried to prevent for the past three years.
"Denial means pre-emptive war as a last resort".More news: Prince George asks Santa for police auto on dad's Finland trip
"Despite persistent sanctions and pressure by the U.S. and other hostile forces, my government concentrates all its efforts on improving people's livelihood and providing them with a better future", the North Korean Permanent Mission to the United Nations said in a statement on 14 November. "The pre-emption is becoming more likely as their technology matures", Graham told CBS. The Chinese are trying, but ineffectively.
In September, it conducted its sixth and most powerful nuclear test.
It is scheduled to last five days and comes less than a week after the rogue state's latest intercontinental ballistic missile test, which Pyongyang claimed was capable of hitting the U.S. mainland.More news: Critics Bash First Lady Melania Trumpâ??s White House Christmas Decorations
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