Seoul and Washington are slated to wrap up their joint military drills on Saturday, but the two Koreas are likely to continue their standoff, with Pyongyang expected to carry out another nuclear test ahead of its ruling party convention in early May.

While it is common for tension to peak during the drills and subside afterward, it is expected to continue this time as South Korea braces for a North Korean nuclear test.

The South Korean Defense Ministry said Tuesday that the military has been on constant lookout for a fifth nuclear test carried out by Pyongyang. A test is thought to be imminent in light of North Korean leader Kim Jong-un’s order to conduct a nuclear warhead test as soon as possible.

“The military believes that the North can carry out a surprise test whenever they decide to, and is on constant alert,” said ministry spokesman Moon Sang-kyun. “The Kim leadership’s resolve (to carry out the test) is the key factor in this matter.”

In light of the North’s nuclear testing and long-range rocket launch earlier in the month, the allies had touted this year’s annual Key Resolve command-post based exercise and Foal Eagle field training with the U.S. to be the largest ever in terms of size and strategic assets deployed.

The USS John C. Stennis strike group, led by the 103,000-ton supercarrier, came to Busan last month to participate in the joint drills. The drills had included the Ssangyong amphibious landing drill, which included troops from Australia and New Zealand, along with preemptive strike simulations against the North Korean leadership.

Experts like Yang Moo-jin, a professor at the University of North Korean Studies, say that Pyongyang will likely conduct the test to both boast its nuclear strike capacities and decorate its young leader before the ruling Workers’ Party of Korea holds its first congress in 36 years.

Pyongyang has recently been boastfully demonstrating its arsenal, including its KN-11 submarine ballistic missile, which underwent a partially successful test launch last week.

The South Korean military has played down its significance, pointing at its abnormally short flight range of 30 kilometers. But foreign-based experts, including IHS Jane’s Karl Dewey, said that such short range may have been deliberate to only test certain design goals.

Experts agree that the test, while far from Pyongyang’s claims of “complete success,” at least demonstrated its capacity to conduct a cold launch of an SLBM underwater.

Local media also reported that the North appears to be preparing for a launch of its intermediate-range Musudan missile. Earlier in the month, Pyongyang conducted its first launch of the Musudan which ended in a failure.

Seoul’s Defense Ministry, however, said it had not received such reports and that it expects the North will take some time to fix the technological errors that may have been revealed in the botched launch.

“Another failed launch before the party convention will have a huge impact (on the North Korean leadership), so I wouldn’t be sure that the North will hurriedly carry out another launch,” said a military official.

By Yoon Min-sik  (minsikyoon@heraldcorp.com)