A former senior Pentagon official has warned that the situation on the Korean Peninsula could become "very dangerous in the next month or two," where an incident involving North Korea could spiral into a second Korean War, dragging Japan and China into it.

"If after January, North Korea goes back to testing ICBMs, which is what it was doing until it stopped in November 2017, then it's quite possible (President Donald) Trump will attack North Korea," Graham Allison, a former assistant secretary of defense under President Bill Clinton, said in an interview in Tokyo.

Earlier this month, North Korea said the United States can expect a "Christmas gift" if there is no breakthrough in stalled denuclearization talks between the two countries by year-end.

(Graham Allison pictured at an interview on Dec. 12, 2019.)

Pyongyang has been pushing Washington to offer a deal with significant sanctions relief, warning that without U.S. flexibility, it will take a "new way," which experts think may indicate restarting nuclear or intercontinental ballistic missile tests.

Officials in Northeast Asia are on alert with U.S. Pacific Air Forces Commander General Charles Brown suggesting Dec. 18 that North Korea's "gift" could be a long-range ballistic missile or an announcement of restarting the tests.

To indicate its seriousness, North Korea quickly followed the threat with two tests on Dec. 8 and Dec. 14 at the Sohae Satellite Launching Ground, which it called a "very important test" and "a crucial test" without elaborating.

Trump has hinted the United States could use military force against North Korea "if we have to." Washington has been calling on Pyongyang to follow through on its commitments to denuclearize and refrain from testing long-range ballistic missiles that could strike the United States.

Allison, now a professor of government at Harvard University, said a U.S. attack on North Korea's nuclear and missile launch pads could lead to a retaliatory attack against Seoul, which he said will likely ensure a U.S.-South Korean military response.

"And then this could trigger a second Korean War," he said.

(North Korea's "super-large multiple rocket launchers" test-fired on Oct. 31, 2019.)[Korean Central News Agency/Kyodo]

Aside from North Korea, the risk of Taiwan sparking a military confrontation between the United States and China has increased, according to Allison.

Hong Kong's months-long pro-democracy movement may encourage Taiwan to ramp up efforts toward full independence from China, he said.

If military intervention by China, which considers territorial integrity with Taiwan "a core interest," leads to a similar U.S. response, he said, Japan -- which has U.S. bases -- will be confronted with the possibility of becoming involved.

The scholar said Washington and Beijing are "precisely on script" toward the "the grandest collision of all times" in what he calls "Thucydides's Trap."

It describes the dynamic when a rising power threatens to displace an established power, leading "almost always" both to war. Escape can be difficult as the wars can be triggered by third parties.

Allison urged Japan, as a key U.S. ally and the world's third-largest economy, to be more active in international affairs to prevent a war between the United States and China.

"It should be playing an active role, not as a favor to China or the U.S., but to say simply, 'If you folks have a war, we will be victims of that war, so we're speaking up for ourselves,'" he said.

"As the seesaw of power has shifted with China's growth, the U.S. is going to need some partners on its side of the seesaw to keep things balanced."