WASHINGTON -- The United States is still analyzing the nature of North Korea's last missile test that probably involved an intercontinental ballistic missile (ICBM), a Pentagon spokesperson said Tuesday, amid reports that Pyongyang may have falsely claimed success in developing a new ICBM.

John Kirby, however, said the US continues to remain concerned about North Korea's efforts to advance its nuclear and ballistic missile capabilities.

"We are still analyzing this last test," the department press secretary said when asked if the US was concerned about the capability of the North Korean missile involved in the latest launch.

North Korea fired an ICBM on Thursday (Seoul time), which it later said flew 1,090 kilometers at a top altitude of 6,248 km.

Experts in Seoul and Washington have noted the missile, when launched at the right angle, would have traveled at least 13,000 km, enough to reach the mainland US.

Pyongyang claims the missile launched was its latest and largest Hwasong-17 with a maximum range of 15,000 km.

The South Korean defense ministry, however, has said the North appears to have fired an earlier model, the Hwasong-15 to disguise its failure in its initial test launch of the Hwasong-17 on March 16.

"I will just tell you that we assess that that launch was a probable ICBM and we continue to analyze the test in close coordination with our allies and partners to include the South Koreans," Kirby said when asked about the South Korean assessment of the latest North Korean missile launch, adding, "I don't have an update for you beyond that."

Still, he said the US remains concerned about North Korea's continued efforts to advance its nuclear and ballistic missile capabilities.

"We remain concerned about the North Koreans, their attempt to continue to improve their nuclear capability, as well as their ballistic missile capability. It's provocative. It poses a threat to security on the peninsula and to the region, to our allies and partners," he said.

North Korea has so far staged 12 rounds of missile firings this year, including seven rounds in January alone that marked the largest number of missile launches it conducted in a single month.

Pyongyang also remains unresponsive to US overtures for dialogue, while staying away from denuclearization talks since late 2019. (Yonhap)