WASHINGTON - US President Donald Trump on Monday put the Democratic People's Republic of Korea back on the list of state sponsors of terrorism, a designation that allows the United States to impose more sanctions but one that also could backfire.

The Republican president, who has traded personal insults with DPRK leader Kim Jong-un but has not ruled out talks, said the Treasury Department will announce additional sanctions against the DPRK on Tuesday.

The designation came a week after Trump returned from a 12-day, five-nation trip to Asia in which he made containing Pyongyang's nuclear ambitions a centerpiece of his discussions.

"In addition to threatening the world by nuclear devastation, North Korea has repeatedly supported acts of international terrorism, including assassinations on foreign soil," Trump told reporters at the White House.

"This designation will impose further sanctions and penalties on North Korea and related persons and supports our maximum pressure campaign to isolate the murderous regime."

Experts say the designation will be largely symbolic, as DPRK is already heavily sanctioned by the US.

South Korea's spy agency said on Monday that the DPRK may conduct additional missile tests this year to improve its long-range missile technology.

A US intelligence official who follows developments in the DPRK expressed concern that the move could backfire, especially given that the basis for the designation is arguable.

The official, speaking on condition of anonymity, said Kim could respond in a number of ways, including renewing missile or nuclear tests in "a very volatile environment".

China has emphasized many times that the essence of the Korean Peninsula nuclear issue is about security. "Only by addressing the reasonable security concerns of all sides in a balanced way through dialogue can we find a fundamental solution to peacefully resolve the Peninsula nuclear issue," Foreign Ministry spokesman Geng Shuang said on Nov 16.

"That is why China has raised the suspension-for-suspension initiative and the dual-track approach, which we believe would be the most pragmatic, feasible, sensible and reasonable proposal under the current circumstance," he said.

The dual suspension calls for the DPRK to suspend its nuclear and missile activities in exchange for the suspension of large-scale US-South Korea military drills, while the dual-track approach calls for the denuclearization of the peninsula and the establishing of a peace mechanism.

"It will not only help ease the current tense situation, but also address the most pressing security concerns of all parties, create opportunities and conditions for resuming peace talks, and find a breakthrough out of the current stalemate," Geng said.

US Secretary of State Rex Tillerson said Washington still hopes to find a diplomatic solution to the simmering crisis.

"We still hope for diplomacy," Tillerson told a White House press conference. "This is all part of continuing to turn this pressure up," he said.

The US has designated only three other countries - Iran, Sudan and Syria - as state sponsors of terrorism.

The DPRK was put on the US terrorism-sponsor list for the 1987 bombing of a Korean Air flight that killed all 115 people aboard. But the administration of former President George W. Bush, a Republican, removed Pyongyang in 2008 in exchange for progress in denuclearization talks.

China Daily - Reuters - AP - AFP