A White House official expressed confidence Tuesday that the United States is keeping an "appropriate" defensive posture against North Korean threats, amid tensions heightened by Pyongyang's continued weapons tests and hardening rhetoric.

John Kirby, the National Security Council coordinator for strategic communications, made the remarks in response to a question of whether there has been a change in the North's military posture following its tough rhetoric against the South that spawned speculation that Pyongyang might be inclined towards preparing for conflict.

"I want to be careful. We don't get into intelligence assessments," Kirby told a press briefing. "But we're watching this very closely and I would just tell you that we remain confident that the defensive posture that we are maintaining on the peninsula was appropriate to the risk."

The North has ratcheted up tensions as it recently launched what it called a solid-fuel intermediate-range ballistic missile tipped with a hypersonic warhead, and tested a claimed underwater nuclear weapons system. It also branded the South as the "invariable principal enemy."

Asked to comment on the report on Russian President Vladimir Putin's possible trip to the North this year, Kirby reiterated Washington's concerns over burgeoning military ties between Pyongyang and Moscow.

"What's concerning to us is this increasing relationship, the deepening relationship between North Korea and Russia because obviously Mr. Putin stands to benefit from it as he not only gets ballistic missiles and using them for use in Ukraine, but also artillery shells," he said.

"We're watching this very closely ... North Korea's own pursuit of advanced military capabilities, and what concerns us is not just Mr. Putin's ability to benefit from this relationship, but (North Korean leader) Kim Jong-un's ability to benefit from this relationship and what that means for peace and security in that region," he added.

After North Korean Foreign Minister Choe Son-hui's trip to Moscow last week, her office said Putin had expressed willingness to visit the North at "an early date." Later, Kremlin spokesperson Dmitry Peskov told local media that Putin's visit to the North is unlikely to take place in the next two months before the March presidential election, according to TASS, a Russian state-run outlet.

Responding to a question of whether Russia has used more North Korean ballistic missiles against Ukrainian targets following earlier occasions, Kirby said, "They have."

The official earlier revealed that the North supplied Russia with several dozen ballistic missiles, some of which were used to attack Ukraine on Dec. 30, Jan. 2 and Jan. 6.

In a separate briefing, Pentagon Press Secretary Maj. Gen. Patrick Ryder urged the North to return to dialogue, as he addressed a question of what scenarios the US is preparing for with regards to the threats from the North's nuclear weapons.

"We've been very public on our commitment to working with allies and partners in the region to deter and help stabilize the security of the region," he said. "Any type of destabilizing acts are unwarranted (and) uncalled for, and we will continue to call on North Korea to return to the diplomatic table." (Yonhap)