The decision comes days after the conclusion of US President Donald Trump's second summit with North Korean leader Kim Jong Un in Hanoi, which ended without a formal agreement but with both sides suggesting they would keep talking.

During a Saturday phone call between South Korean Defence Minister Jeong Kyeong-doo and his US counterpart Patrick Shanahan, "both sides decided to conclude the Key Resolve and Foal Eagle series of exercises," according to a Pentagon statement.

The two allies will instead carry out "adjusted outside manoeuvre trainings and united command exercises to continue firm military readiness", Seoul's defence ministry said Sunday.

Foal Eagle is the biggest of the regular joint exercises held by the allies, and has always infuriated Pyongyang, which condemned it as preparations for invasion.

In the past, it has involved 200,000 South Korean forces and some 30,000 US soldiers.

It is accompanied by Key Resolve, a computer-simulated war game conducted by military commanders which usually begins in March and runs for about 10 days.