US steps up pressure on North Korea; plans to impose economic sanctions

The US has said it also plans to activate a missile defence system in South Korea

The US has said it plans to activate a missile defence system in South Korea "within days" and tighten economic sanctions against North Korea amid rising fears about Pyongyang's military advances.

Speaking to members of the US Congress on Wednesday, Admiral Harry Harris, Commander of the US Pacific Command, said the Terminal High Altitude Area Defence (THAAD) would be "operational in the coming days to be able to better defend South Korea against the growing North Korea threat".

North Korea has vowed to conduct more missile and nuclear tests.

Admiral Harris said the system is designed to bring North Korean leader Kim Jong-un "to his senses, not to his knees".

The arrival of the defence equipment at the Seongju County in South Korea on Wednesday met with protests by locals, BBC reported.

It also angered China, which fears the system's radar capabilities will affect its own military security, and changes the balance of power in the region.

After repeated missile tests by North Korea, including a failed ballistic missile test on April 16 and threats of further nuclear tests, US Vice President Mike Pence warned North Korea not to "test" President Donald Trump.

On Tuesday, a US submarine -- the USS Michigan -- joined a group of warships in the Korean peninsula led by aircraft carrier the USS Carl Vinson.

North Korea, meanwhile, threatened to sink the aircraft carrier and launch a "super-mighty pre-emptive strike" against what it called US aggression.

After a special briefing for all 100 US senators, top US officials announced President Donald Trump's strategy on North Korea.

"The President's approach aims to pressure North Korea into dismantling its nuclear, ballistic missile, and proliferation programmes by tightening economic sanctions and pursuing diplomatic measures with our allies and regional partners," said a joint statement by US Secretary of State Rex Tillerson, Defense Secretary Jim Mattis and Director of National Intelligence Dan Coats.

The US already has extensive sanctions in place on North Korea, including a blanket ban on trade and a blacklist of anyone dealing with North Korea.