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.

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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 signaled 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.

In pictures: North Korea military drill Show all 8 1 /8 In pictures: North Korea military drill In pictures: North Korea military drill North Korea's leader Kim Jong Un watches a military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video

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 to violence including an offensive attack or a defensive, retaliatory attack.