By Christine Kim and Ben Blanchard

SEOUL/BEIJING (Reuters) – Tension on the Korean peninsula eased slightly on Monday as South Korea’s president said resolving North Korea’s nuclear ambitions must be done peacefully and U.S. officials played down the risk of an imminent war.

Concern that North Korea is close to achieving its goal of putting the mainland United States within range of a nuclear weapon has caused tension to spike in recent months.

U.S. President Donald Trump warned last week that the U.S. military was “locked and loaded” if North Korea acted unwisely after threatening to land missiles in the sea near the U.S. Pacific territory of Guam.

“There must be no more war on the Korean peninsula. Whatever ups and downs we face, the North Korean nuclear situation must be resolved peacefully,” South Korean President Moon Jae-in told a meeting with senior aides and advisers.

“I am certain the United States will respond to the current situation calmly and responsibly in a stance that is equal to ours,” he said.

U.S. Defense Secretary Jim Mattis and Secretary of State Rex Tillerson sent a conciliatory message to North Korea in an op-ed piece in the Wall Street Journal on Sunday.

“The U.S. has no interest in regime change or accelerated reunification of Korea. We do not seek an excuse to garrison U.S. troops north of the Demilitarized Zone,” the officials said, addressing some of Pyongyang’s fears that Washington ultimately intends to replace the reclusive country’s leadership.

The article took a softer tone on North Korea than the president, who warned Pyongyang last week of “fire and fury” if it launched an attack.

Mattis and Tillerson underlined that the United States aims “to achieve the complete, verifiable and irreversible denuclearization of the Korean Peninsula and a dismantling of the regime’s ballistic-missile programs.”

“While diplomacy is our preferred means of changing North Korea’s course of action, it is backed by military options,” they said.

The United States is adopting a policy of “strategic accountability” towards North Korea, the officials wrote, but it is not clear how this significantly differs from the “strategic patience” Korea policy of former President Barack Obama.

A global index of stocks rose, after fears of a U.S.-North Korea nuclear standoff had driven it to the biggest weekly losses of 2017, while the dollar also strengthened.

U.S. Central Intelligence Agency Director Mike Pompeo said North Korean leader Kim Jong Un might conduct another missile test but talk of being on the cusp of a nuclear war was overstating the risk.

“I’ve seen no intelligence that would indicate that we’re in that place today,” Pompeo told “Fox News Sunday”.

However, North Korea reiterated its threats, with its official KCNA news agency saying “war cannot be blocked by any power if sparks fly due to a small, random incident that was unintentional”.

“Any second Korean War would have no choice but to spread into a nuclear war,” it said in a commentary.

The United States and South Korea remain technically still at war with North Korea after the 1950-53 Korean conflict ended with a truce, not a peace treaty.

MISSILE DOUBTS

South Korean Vice Defence Minister Suh Choo-suk agreed North Korea was likely to continue provocations, including nuclear tests, but did not see a big risk of the North engaging in actual military conflict.

Suh again highlighted doubts about North Korea’s claims about its military capability.

“Both the United States and South Korea do not believe North Korea has yet completely gained re-entry technology in material engineering terms,” Suh said in remarks televised on Sunday for a Korea Broadcasting System show.

Ukraine denied on Monday that it had supplied defense technology to North Korea, responding to an article in the New York Times that said North Korea may have purchased rocket engines from Ukrainian factory Yuzhmash.

Tension in the region has risen since North Korea carried out two nuclear bomb tests last year and two intercontinental ballistic missile tests in July, tests it often conducts to coincide with important national dates.

Tuesday marks the anniversary of Japan’s expulsion from the Korean peninsula, a rare holiday celebrated by both the North and the South. Moon and Kim, who has not been seen publicly for several days, are both expected to make addresses on their respective sides of the heavily militarised border.

Trump has urged China, the North’s main ally and trading partner, to do more to rein in its neighbor, often linking Beijing’s efforts to comments around U.S.-China trade. China strenuously rejects linking the two issues.

Trump will issue an order later on Monday to determine whether to investigate Chinese trade practices that force U.S. firms operating in China to turn over intellectual property, senior administration officials said on Saturday.

Chinese Foreign Ministry spokeswoman Hua Chunying said that Beijing has said many times the essence of China-U.S. trade and business ties is mutual benefit and that there is no future in any trade war between China and the United States.

“The (Korean) peninsula issue and trade and business issues are in a different category from each other,” Hua added. “On these two issues, China and the United States should respect each other and increase cooperation. Using one issue as a tool for exerting pressure on another is clearly inappropriate.”

China’s Commerce Ministry issued an order on Monday banning imports of coal, iron ore, lead concentrates and ore, lead and sea food from North Korea, effective from Tuesday.

The move followed the announcement of U.N. sanctions against North Korea this month which have to be enforced within 30 days by member states.

U.S. Joint Chiefs of Staff Chairman Joseph Dunford told South Korea’s Moon in a meeting on Monday that U.S. military options being prepared against North Korea would be for when diplomatic and economic sanctions failed, according to Moon’s office.

(Writing by Lincoln Feast and Alistair Bell; Editing by Raju Gopalakrishnan and James Dalgleish)