US President Donald Trump and South Korea's leader Moon Jae-In agreed Monday to remove limits on the payload of the South's missiles, Seoul's presidential office said, as the UN Security Council met to discuss a response to Pyongyang's sixth and most powerful nuclear test.

 

The two leaders in a phone call "agreed to lift the cap on missile payload of South Korea as an effective countermeasure" against Pyongyang's test on Sunday of what it described as a hydrogen bomb designed for a long-range missile, the presidential office said in a statement.

 

Seoul was previously restricted to a maximum warhead weight of 500 kilograms (1100 pounds) on its ballistic missiles, according to a bilateral agreement with the United States signed in 2001.

 

Tensions have mounted on the Korean peninsula following a series of missile launches by the North, including two launches of intercontinental ballistic missiles (ICBMs) that apparently brought much of the US mainland into range.

 

As Pyongyang's stand-off with the US escalates, calls are also increasing in South Korea for Seoul to build nuclear weapons of its own to defend itself against the North.

 

The South, which hosts 28,500 US troops to defend it, is banned from building its own nuclear weapons under a 1974 atomic energy deal it signed with Washington, which instead offers a "nuclear umbrella" against potential attacks.

 

South Korea's defense ministry said it was already strengthening its national defenses, in part by deploying more US-made Terminal High-Altitude Area Defense (THAAD) missile launchers.

 

Seoul also fired an early-morning volley of ballistic missiles Monday in an exercise simulating an attack on the North's nuclear test site.