The Democratic People's Republic of Korea (DPRK) and the U.S. had made no progress in talks on why a South Korean warship sank in March, the official KCNA news agency reported Wednesday.

The seventh round of senior colonel-level military talks were held in Panmunjom on Wednesday over the sinking, which South Korea has blamed on the DPRK.

According to the KCNA, the DPRK strongly urged the U.S. to accept its previously suggested proposal of bringing evidence for the "Cheonan" case to Panmunjom to jointly verify it. However, the U.S. side repeatedly revealed its intention to "make the results of joint investigation an established fact."

During the talks, the DPRK cast doubt on the U.S. side's resolution in probing the "Cheonan" case according to the agreed agenda, and the U.S. representatives remained silent on the reason for its reluctance to conduct a joint investigation into the evidence, the KCNA reported.

"There is a limit to the patience of the army and people of the DPRK," the DPRK side was quoted as saying by the KCNA.

If the U.S. side refused to meet this "last demand" of the DPRK, the DPRK would have no option but to "bring to light the true nature" of the event, which was "orchestrated" by the U.S. and South Korea, the KCNA quoted the DPRK officials as saying.

On March 26, South Korea's 1,200-ton "Cheonan" vessel with 104 crew members aboard sank near the maritime border with the DPRK after an unexplained explosion. Only 58 sailors were rescued.

South Korea issued in May the result of its investigation, which alleged the "Cheonan" was sunk by a DPRK torpedo. The claim was immediately rejected by the DPRK National Defence Commission, which proposed to send an inspection group to South Korea to verify the evidence. However, the request was rejected by South Korea.