US President Donald Trump and South Korean President Moon Jae-in said they plan to revise a 43-year-old joint treaty that caps the number and range of South's ballistic missiles, Moon's office said on Saturday.

"The two leaders agreed to the principle of revising the missile guideline to a level desired by South Korea, sharing the view that it was necessary to strengthen South Korea's defense capabilities in response to North Korea's provocations and threats," South Korea's presidential Blue House said.

South Korea, which hosts 28,500 US troops, is banned from building its own nuclear weapons under a 1974 atomic energy deal it signed with Washington, which was revised in 2012.

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Under the treaty, Seoul is restricted to possessing ballistic missiles with a maximum range of 800 kilometers (500 miles) and a payload of 500 kilograms (1,100 pounds). Washington, in turn, offers a "nuclear umbrella" against potential attacks.

The US and South Korean forces are nearing the end of the 10-day annual Ulchi Freedom Guardian joint exercises. On Thursday US heavy bombers and stealth jet fighters took part in a joint live fire drill in South Korea intended as a show of force.

Threats from the north

Trump and Moon, speaking by phone on Friday, also discussed North Korean's "continued destabilizing and escalatory behavior," the White House said in a statement.

Trump - who has warned that the US military is "locked and loaded" in the event of further North Korean provocation - reacted angrily to the latest missile test.

Pyongyang fired an intermediate-range Hwasong-12 over Japan on Tuesday. It said this was a "curtain-raiser" for the North's "resolute countermeasures" against ongoing US-South Korean military drills.

North Korea has been working to develop a nuclear-tipped missile capable of hitting the US and has recently threatened to land missiles near the US Pacific territory of Guam.

jbh/sms (AFP, Reuters)