John Bacon

USA TODAY

South Korea was bracing for a possible show of strength from North Korea to mark the 85th anniversary of the Korean People's Army on Tuesday as tensions continued to rise in the region.

The South Korean news agency Yonhap reported "speculation that (Pyongyang) may conduct its sixth nuclear test or launch a long-range missile." A spokesman for South Korea's unification ministry, however, said Monday that no alarming activity had been detected.

"When it comes to the anniversary, there have been no unusual signs in North Korea," ministry spokesman Lee Duk-haeng said.

Pyongyang has issued a steady stream of threats aimed at the U.S. and its allies. The pattern continued Monday as North Korea's defense minister warned that "precise and advanced striking means" targeting the U.S. and its allies already are in place. Pyongyang previously threatened to sink the USS Carl Vinson, an aircraft carrier en route to the Korean Peninsula.

"Our nuclear weapons capable of striking U.S. military bases in Asia-Pacific areas and the U.S. homeland are fully prepared to be fired from launchers," Pak Yong-sik said at a meeting of Pyongyang's military leaders, according to the North Korea's official Korean Central News Agency.

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President Trump has warned that the U.S. has not ruled out a military strike to blunt Pyongyang's ambitions and has been lobbying China to increase pressure on North Korean leader Kim Jong Un. North Korea's closest ally has called for restraint. Chinese leader Xi Jinping, in a phone conversation with Trump on Monday, stressed that compromise was needed to "denuclearize the Korean Peninsula as soon as possible," China's Xinhua news agency reported.

The White House said Trump "criticized North Korea’s continued belligerence and emphasized that Pyongyang’s actions are destabilizing the Korean Peninsula."

Secretary of State Rex Tillerson said Monday that he will chair a special meeting of the U.N. Security Council on Friday to discuss denuclearization of the peninsula. He said the council will discuss ways to "maximize the impact" of U.N. sanctions and other measures.

Relations between the U.S. and North Korea have grown more strained in recent months. Pyongyang has defied U.N. directives by continuing to conduct nuclear and ballistic missile testing, and Kim has expressed outrage at massive joint military exercises conducted by the U.S. and South Korea.

Last week, Vice President Pence visited South Korea and Japan, warning that "the era of strategic patience is over." He said any military strike by North Korea would draw an "overwhelming and effective" response from the United States. The U.N. Security Council also weighed in, condemning North Korea over its latest missile test earlier this month. The statement included a call for dialogue and drew China's support.

On Saturday, a U.S. citizen was arrested at Pyongyang's airport, raising to three the number of Americans now detained by Kim Jong Un's regime. Park Chan-mo, the chancellor of the Pyongyang University of Science and Technology, told the Associated Press that Tony Kim, 58, taught accounting at the university for about a month and was detained by officials as he was trying to fly to China with his wife.

Other Americans being held in North Korea include Ohio native Otto Warmbier, a University of Virginia student who was arrested in January 2016 while he was on a tour of North Korea, and Kim Dong Chul, who was arrested in October 2015 while in North Korea on business.

Warmbier was accused of committing a "hostile act" for allegedly trying to steal a political banner and was sentenced in March 2016 to 15 years hard labor. Kim was accused of stealing military secrets and is serving a 10-year sentence.