SEOUL (AP):  The South Korean and US militaries on Thursday announced that they were postponing their annual joint drills due to concern about a viral outbreak that has infected soldiers in both countries' armed forces, put many troops in quarantine and closed base facilities.

Twenty-two South Korean soldiers and one American service member in South Korea have tested positive for the new coronavirus, which has infected about 1,770 people in the Asian country, the largest outbreak outside mainland China.

The allies have previously suspended or scaled back their regular military exercises, but that was part of diplomatic efforts to disarm North Korea, which views the training as a rehearsal for an invasion.

It's the first time that the allies have put off their drills due to concerns about an infectious disease, according to the South Korean Defence Ministry.

In a joint news conference, South Korean and US military officers said their joint drills planned for the first half of this year will be put off until further notice.

South Korean military chief Park Han-ki proposed the delay out of concerns for troop safety and Robert Abrams, the commander of the US military in South Korea, accepted Park's proposal based on the severity of the virus outbreak, said Kim Joon Rak, a spokesman at the South Korean Joint Chiefs of Staff.

Lee Peters, a US military spokesman, said the postponement decision "was not taken lightly" and that two countries' alliance remains "ironclad and unbreakable".

"Despite the postponement of combined training, the ROK-US alliance remains committed to providing a credible military deterrence and maintaining a robust combined defense posture to protect the ROK against any threat," he said. ROK stands for the Republic of Korea.

South Korea boasts a 600,000-strong military, while the US has 28,500 troops in the country and those troops are at particular risk due to the close quarters at the bases where they are stationed.

In recent days, South Korea suspended some unilateral field training, placed 9,990 troops under quarantine and banned most of its enlisted soldiers from leaving their bases. The US military closed some amenities at several bases and was urging its personnel to avoid handshakes and large gatherings if possible.

Experts say the postponement of the drills was inevitable because the potential spread of the virus into military barracks could significantly weaken military readiness.

North Korea has not publicly reported any case of the virus, but many experts say the the country also likely reduced its own military training as it's preoccupied with guarding against the virus.

An epidemic in North Korea could cause a devastating consequence because of its dilapidated medical and health care infrastructures, experts say.

This makes it unlikely that North Korea would launch any major provocation anytime soon though leader Kim Jong Un in late December threatened to unveil "a new strategic weapon" soon, said analyst Kim Dae-young at the Korea Research Institute for National Strategy in South Korea.

The US and South Korea were supposed to hold their major springtime drills in March, mostly tabletop exercises and simulations. The drills were revised to create more space in nuclear disarmament diplomacy with North Korea and replaced much bigger exercises that had particularly irritated Pyongyang.

Yang Wook, a military expert who teaches at South Korea's Hannam University, said the springtime command post drills involve officers gathering at a small place so it's easier for them to catch the virus if there is a patient.

"If they all wear gas masks and train together, they could be safe. If they can't do so, it's not a bad idea to be more cautious," Yang said.