A U.S. official reportedly said North Korea appears to have tested a modified version of an existing Hwasong-15 intercontinental ballistic missile(ICBM), contrary to the North's claim that it launched a new Hwasong-17.

The Washington Post on Monday quoted the official as saying that the missile in question appeared to be a modified version of the Hwasong-15, an older model that is slightly smaller than the Hwasong-17.

The official, who spoke on the condition of anonymity, reportedly said the missile was modified to fly higher and farther than the last ICBM North Korea tested in 2017.

The official said the latest test still showed that the North is making incremental progress in improving its ICBM capability.

The assessment echoes recent reports that South Korea and the U.S. concluded North Korea’s launch was of an existing Hwasong-15 ICBM, not a new Hwasong-17 ICBM.

North Korea tested its first ICBM in over four years last Thursday and claimed the next day that it was a new Hwasong-17 ICBM.