North Korean leader Kim Jong-un (2nd from left) attending the commissioning ceremony on Wednesday of a newly built "tactical nuclear attack submarine." (Yonhap)

North Korea may test fire a submarine-launched ballistic missile to show the effectiveness of its new tactical nuclear submarine launched earlier this month, a US monitor said Monday.

Beyond Parallel, a project of the Washington-based Center for Strategic and International Studies, also noted that Pyongyang may request submarine or SLBM-requested technology from Russia during leader Kim Jong-un's high-profile trip to Russia.

"The logical next step for North Korea is a missile launch from the submarine to demonstrate to the world that the vessel is operational," it said in a report published on its website.

"When such a test will take place is unclear," it added.

Pyongyang reported Friday that it has launched a newly built "tactical nuclear attack submarine," named the 'Hero Kim Kun Ok,' adding that a commissioning ceremony, held Wednesday, was also attended by leader Kim.

The US monitor noted that North Korea's SINPO-class ballistic missile submarine was first observed in July 2014, and that the vessel was used to test an SLBM nearly 16 months after in November 2015.

"How North Korea will proceed with its ballistic missile submarine program is unclear at this time," it said. "What is clear, however, is that North Korea is continuing to slowly develop its operational ballistic missile capabilities."

The report underlined that North Korea's efforts to advance its submarine program may be accelerated following Kim's imminent meeting with Russian President Vladimir Putin, "where the North Korean leader may request the transfer of modern SSB and SLBM technology from Russia."

North Korea reported earlier that Kim will soon visit Russia to meet with Putin at the invitation of the Russian president.

US officials have said that a Kim-Putin meeting would be part of what they called "actively advancing" negotiations between Pyongyang and Moscow for an arms deal, under which North Korea is widely expected to request for advanced military technology from Russia in exchange for artillery shells and other weapons to be used in Russia's ongoing war against Ukraine.

US special envoy for North Korea Jung Pak said earlier in the day that a Kim-Putin summit may be the "final step" before North Korea begins providing significant quantities of weapons to Russia to be used against Ukraine. (Yonhap)