South Korea and the United States kicked off joint military drills Monday, South Korea’s Yonhap news agency reported, despite warnings and weapons tests from North Korea in recent weeks.

The two allies will stage drills with a command-post exercise mostly involving computer simulations, not mobilization of troops or military equipment, for about two weeks, while also testing South Korea’s capabilities in retaking operational control over its forces from the United States during wartime, Yonhap reported, citing unidentified sources.

South Korea’s Defense Ministry had earlier said the two countries were preparing to hold the exercises, but did not confirm when they would start.

“Our joint exercise to verify (Seoul’s) capabilities for its envisioned retaking of wartime operational control is being prepared,” a ministry official was quoted as saying.

Asked about the time frame for the exercises, a U.S. Forces Korea (USFK) spokesman declined to confirm if they had begun as scheduled, citing “standard operating procedure, and in order to preserve space for diplomacy to work.”

“I can tell you that we continue to train in a combined manner at echelon while harmonizing our training program with diplomatic efforts by adjusting four dials: size, scope, volume and timing,” USFK spokesman Col. Lee Peters said via email.

The exercises come in the wake of warnings from nuclear-armed North Korea. The North has long denounced the joint exercises as a rehearsal for invasion, a charge the U.S. and its allies have denied.

Over a span of eight days recently, Pyongyang conducted three tests of short-range ballistic missiles in violation of U.N. sanctions and some observers say the joint drills could trigger more provocations from the North.

It characterized one of the test-firings as a “solemn warning” against the military exercises and Seoul’s purchase of high-tech F-35 stealth fighter jets from Washington.

The Yonhap report also said Seoul and Washington will bolster surveillance for potential launches from Pyongyang during the joint drills.

The North Korea also hinted last month that long-stalled working-level denuclearization talks with the United States, due to be restarted soon, could be halted and nuclear and missile tests restarted if the U.S. goes ahead with the joint exercises.

U.S. President Donald Trump, who has met with North Korean leader Kim Jong Un three times, including in late June at the Demilitarized Zone separating the two Koreas, has said the working-level nuclear negotiations will kick off soon. After his first meeting with Kim, he pledged to halt the “expensive” exercises, which he has derisively called “war games.”

The allies have scrapped or scaled down their large-scale joint military drills — Key Resolve, Foal Eagle and Ulchi Freedom Guardian.

In March, the new 19-2 Dong Maeng (alliance) exercise was launched as a replacement for their springtime Key Resolve and Foal Eagle exercises.

Observers say Trump is betting that by keeping the joint exercises low-key, the U.S. can still convince the North to return to the bargaining table once the drills wrap up.