SINGAPORE (BLOOMBERG) - North Korea has added a structure to a factory linked to the production of intercontinental ballistic missiles, NBC News reported, raising concerns the reclusive country will resume testing weapons that can reach the United States.

The commercial satellite images from Planet Labs show a temporary structure added to the site that can accommodate the raising of a launcher arm for such long-range missiles, according to NBC.

The news report cited an analysis by Dr Jeffrey Lewis, director of the East Asia Nonproliferation Programme at the Middlebury Institute of International Studies.

The hermit state has engaged in a series of weapons tests as its leader Kim Jong Un approaches his self-imposed year-end deadline for US President Donald Trump to make a better offer in negotiations.

The two sides recently resumed threats and insults, with North Korea warning that it was preparing a choice of "Christmas" gifts for Mr Trump, depending on his response.

North Korea last launched an intercontinental ballistic missile in November 2017, a breakthrough test that demonstrated Mr Kim's ability to carry nuclear warheads to the entire US mainland.

Mr Kim subsequently declared his nuclear weapons programme "complete" and opened talks with South Korea and later with Mr Trump.