South Korea, the United States and Japan agreed Wednesday to continue joint efforts to put "maximum pressure" on North Korea in order to bring it to the negotiating table.

The three countries strongly condemned the North's launch last week of a ballistic missile with intercontinental range during a video conference of their defense officials, according to the South's Ministry of National Defense.

It was meant to share information on the latest provocation and discuss countermeasures.

They pointed out that the July 4 missile firing was in clear violation of multiple UN Security Council resolutions imposing sanctions on Pyongyang and emphasized the communist regime's development of weapons of mass destruction poses a grave threat to global peace and stability, the ministry said.

The regional powers reaffirmed the importance of coordination to achieve the "complete and irreversible" denuclearization of the Korean Peninsula and coax the North into halting provocations and returning to dialogue.

South Korea was represented by Chang Kyung-soo, acting chief of the ministry's policy planning office. His counterparts were David F. Helvey, US assistant secretary of defense for Asian and Pacific security affairs, and Satoshi Maeda, director general for Japan's defense policy.

The reclusive North claimed that it successfully test-fired an intercontinental ballistic missile, named the Hwasong-14, as Americans marked Independence Day.

Launched on the "maximum-lofted" trajectory, it said, the missile reached an apogee of 2,802 kilometers and flew 933 km for 39 minutes.

But there are growing doubts about whether the North has actually mastered ICBM technology.

It would need at least a few more years to develop an ICBM to strike the US mainland, according to Chang Young-keun, a missile expert at Korea Aerospace University.

Citing an simulated analysis, he said the North fired the missile with a 900-kg warhead on a lofted angle to reduce the maximum altitude and avoid possible technical trouble.

"A simulation showed that its range came to only 6,200 km," Chang said in a report. "If a standard warhead is loaded onto the Hwasong-14 ICBM, it can be used for an attack on Alaska and Hawaii. Its range falls short of a level to hit the US mainland."

The distance between Pyongyang and San Francisco is about 9,000 km.

He said the Hwasong-14 is believed to be 19.5 meters long, with an 11-meter-long and 1.4-meter-diameter first-stage booster.

The North is expected to focus on developing a small warhead in a bid to extend the range of its ICBM, a work likely to take two or three years.

He echoed an assessment by the South's state intelligence agency that it remains unconfirmed whether the Hwasong-14 succeeded in atmospheric re-entry, a key element for an ICBM. (Yonhap)