SEOUL -- South Korea has pressed the U.S. to hand back wartime control of its military, but hesitation on the part of Washington has exposed a rift between the allies over who would command South Korean forces in a crisis.

Gen. Xavier Brunson, the commander of U.S. Forces Korea that is headquartered at Camp Humphreys in Pyeongtaek, South Korea, has expressed reluctance at the idea of returning operational control South Korea, citing North Korea's improved nuclear and missile technology.

"Because the conditions have changed, because we've changed our plan, we have new standards which we have to uphold," Brunson said at a forum in Washington last week.

The U.S. has deployed about 28,000 service members as part of U.S. Forces Korea along with military hardware.

Since the Korean War, the U.S. has led the combined allied command structure responsible for wartime operations on the Korean peninsula. Operational control is held by the head of the United Nations Command, who doubles as the commander of U.S. Forces Korea. Seoul considers holding operational control at the core of achieving a self-reliant national defense.

Seoul and Washington reached an agreement in 2007 to return operational control to the South Korean military. But concerns about South Korea's defense readiness have led to the transfer being postponed.

The administration under South Korean President Lee Jae Myung said it will gain operational control as early as 2028. The government says that South Korea's military capabilities are sufficient and argues that an independent national defense is a fundamental principle in the face of global instability.

The administration of South Korean President Lee Jae Myung seeks to gain wartime operational control of the nation's military as early as 2028.

The U.S. and South Korea have both affirmed a set of conditions that must be guaranteed before operational control can be transferred. They include sufficient defense capabilities of the South Korean military, the ability of the alliance to respond to North Korean nuclear and missile threats, and the stability of the Korean peninsula and the surrounding region.

The day after Brunson spoke, a spokesperson for South Korea's defense ministry expressed a personal view that the transfer of operational control would never be achieved "if the goalposts keep moving." "The principle that control will be transferred only when mutually agreed-upon conditions are met remains unchanged," said the spokesperson.

Some in South Korea say the return of operational control will be postponed longer than anticipated by Seoul. South Korea newspaper Joongang Ilbo reported that the U.S. this year found some of South Korea's defense capabilities inadequate, even after giving a passing grade last year.

Another local newspaper, the Chosun Ilbo, reported that the U.S.-South Korea Security Consultive Meeting could be pushed back to December. The dialogue between top defense officials from both sides is usually held in November. South Korea may be trying to delay the meeting to buy time to persuade the U.S. side to complete one of the procedures for transferring operational control, according to the report.

During the forum at the Gold Institute for International Strategy last week, Brunson also sparked controversy when he suggested that, from the U.N. Command's perspective, South Korean territory starts at a barbed-wire fence at the southern side of the demilitarized zone.

According to South Korea's constitution, the nation's territory consists of "the Korean peninsula and its adjacent islands." Brunson's comment drew fire from the ruling Democratic Party of Korea, which demanded an apology from Brunson for denying South Korea's territorial sovereignty.

The U.N. Command issued a statement Sunday saying that South Korea's sovereignty is not in question. Brunson's remarks were meant to address military and administrative responsibilities and there was no intention to broach the issue of national sovereignty, according to the statement.