Australia is stepping up its role in tightening the net around North Korea, carrying out naval drills with the United States and South Korea to practise intercepting ships suspected of carrying illicit weapons to and from the rogue regime.
Two Anzac Class frigates began the two-day joint exercises on Monday in seas to the South of the Korean peninsula alongside powerful guided-missile destroyers from the other two countries as well as four smaller warships, maritime patrol planes and helicopters.
The crews are rehearsing how to stop and search a suspect ship of any country but the drills are clearly aimed at North Korea, which is not allowed to trade in arms because of several sets of United Nations sanctions.
Defence Minister Marise Payne said the drills would enforce UN Security Council Resolution 2375, concerning "the interdiction of vessels carrying suspicious cargo".
"The multilateral maritime interdiction exercise is an opportunity to practically demonstrate the Australian, ROK and US navies' ability to work together, in support of the rules-based global order," she said.
"Australia has a world-leading maritime interdiction capability and this exercise will enable the sharing of knowledge and skills between the three navies to help prevent the spread of weapons of mass destruction."
Australian frigates HMAS Melbourne and HMAS Parramatta will undertake the training alongside South Korea's Sejong the Great destroyer ship and USS Chafee, an Arleigh Burke-class destroyer.
The training mission came as the Pentagon outlayed the grim choices facing the US and its allies in stopping North Korea, saying that a full ground invasion of the country was "the only way" to be certain it could destroy all of Pyongyang's nuclear weapons.
And US President Donald Trump started his 12-day tour of Asia, during which mustering international determination to stop North Korea's nuclear program is the number one objective, according to a senior US administration official.
The United States wanted to dramatically increase ship interdictions in the most recent round of UN sanctions aimed at reining in Pyongyang's nuclear weapons program. That would have allowed the US and others to use force on the high seas to stop ships suspected of carrying any type of goods whose trade is prohibited by sanctions.
But veto-wielding Security Council members China and Russia stripped out those measures, leaving the noose of interdiction efforts only incrementally tightened, meaning that interdiction can only happen if ships are suspected of carrying arms materials, particularly anything used in the production of weapons of mass destruction and missiles to deliver them.