The American military is ready with a plan to strike North Korean missile sites in a preemptive attack if Donald Trump decides to do so.

The plan involves flying a B-1B heavy bomber from Andersen Air Force Base in Guam accompanied by satellites, drones, higher jets, and aerial refuelling warplanes. Training for the mission has been ongoing, and there have been 11 practice runs for a similar mission since May when the training was accelerated.

“Of the military options … [President Trump] could consider, this would be one of the two or three that would at least have the possibility of not escalating the situation,” retired Admiral James Stavridis, the former Supreme Allied Commander Europe, told NBC.

There are six B-1B bombers positioned in Guam, about 2,100 miles by air to North Korea. The bombers have been heavily used in both Afghanistan and Iraq, and have been updated since then.

The news of the potential operations comes as the relationship between the US and North Korea has become very strained. North Korean leader Kim Jong Un and Mr Trump have engaged in a heated back and forth of threats. Recently, Mr Trump promised “fire and fury” if Mr Kim didn’t stop threatening the United States. In response, Mr Kim’s government signalled they were considering an attack on Guam if Mr Trump didn’t cool his tough talk.

Both countries appear to be more than willing to push the other further and further with the threats, however, in spite of assurance from US Secretary of State Rex Tillerson, who has said that Americans have no reason to worry about an impending war.

Should Mr Trump choose the attack plan that includes the B-1B bomber, they would be targeting approximately two dozen North Korean missile-launch sites, test grounds and other facilities, sources told NBC.

Defense Secretary James Mattis, following the exchange of threats, released a statement saying that the Pentagon was prepared for any escalation of violence including an offensive attack or a defensive, retaliatory attack.

“While our State Department is making every effort to resolve this global threat through diplomatic means,“ the statement said, ”it must be noted that the combined allied militaries now possess the most precise, rehearsed and robust defensive and offensive capabilities on Earth.”