Australia, Canada, Colombia, Denmark, New Zealand, and the Netherlands are also expected to participate in the drills as part of the United Nations command forces, the US Department of Defense said in a statement.
"I am pleased to see that the regime in Pyongyang has certainly demonstrated some level of restraint that we've not seen in the past."
Also at the weekend, North Korea said it was canceling the Wonsan Air Show, which was scheduled for September.
The "accidental" reveal of the two as-yet-untested missiles was in photographs of a factory inspection by leader Kim Jong-un. While qualified, he added: "Maybe, probably not, something positive will come out of it". South Korea is still carefully calculating the next step as to how they wanted to get involved.
These details are unlikely to have been released by mistake, coming just weeks after Donald Trump threatened "fire and fury" on North Korea. It's unclear where the three missiles fired Saturday were targeted.
The two ICBM launches prompted the U.N. Security Council to impose fresh sanctions on Pyongyang that aim to slash the country's $3 billion annual export revenue by a third. The Trump administration has also instituted a formal investigation over China's alleged theft of intellectual property that could result in United States trade penalties.
It's the second major tourist event North Korea has canceled this year.
Tens of thousands of South Korean and U.S. troops are taking part in joint military drills, a largely computer-simulated exercise that runs for two weeks.
North Korea once again chose to ratchet up tensions with the Trump administration Saturday by firing three short-range missiles about 155 miles into the Sea of Japan. Since Pyongyang will never give up its nuclear weapons, it must be persuaded that regime change is not an option for world powers.
It was attributed to a spokesman for the National Peace Committee of Korea, North Korea's official agency for disputes with the south, in a statement carried by the Korean Central News Agency (KCNA).
South Korea's President Moon Jae-in says military action against North Korea can not be carried out without his government's permission.