In a New Year's Day message, the North Korean government called on Koreans in the South and overseas to join it in creating a "powerful nation" to counter a possible U.S. invasion.
"All the Koreans in the north and the south and abroad should approach the reckless and vicious war moves of the U.S. imperialists with high vigilance," the Korean Central News Agency, Pyongyang's foreign news outlet, declared Wednesday, "and deal a telling blow at them by the concerted efforts of the whole nation."
U.S. and South Korean officials say their alliance is strong, though North Korea often has tried to drive a wedge between them.
Anti-American sentiment has been on the upsurge in South Korea, especially after the U.S. military refused to turn over two servicemen accused of killing two schoolgirls in a road accident.
"It can be said that there exists on the Korean Peninsula at present only confrontation between the Koreans in the North and the South and the United States," the New Year's message on the KCNA Web site said.
The English-language message did not mention rising international concern over Pyongyang's decision to reactivate its nuclear facilities at Yongbyon, but stressed the importance of North Koreans uniting around the country's military.
"The United States is now becoming all the more frantic in its moves to stifle the DPRK [North Korea], openly clamoring about a preemptive nuclear attack on it," said the New Year's message.
"If the enemy invades even an inch of the inviolable territory of the DPRK, the people's army and people of the DPRK will wipe out the aggressors to the last man," read a statement a day earlier.
President Bush, on the other hand, said Tuesday that he was confident the standoff could be resolved peacefully.
"This is not a military showdown. This is a diplomatic showdown," Bush said.
Many younger South Koreans view the U.S. military as an army of occupation that prevents national reunification, while the large ethnic Korean population in Japan has long given economic and political support to the North.
Leftist Roh Moo-hyun won the South Korean Dec. 19 presidential election partially by espousing anti-U.S. sentiments. After influential New York Times columnist William Safire proposed pulling U.S. troops out of the peninsula, Roh moderated his statements somewhat.
Nonetheless, Roh on Tuesday warned against "blindly following U.S. policy" toward Pyongyang.
"The United States should consult fully with South Korea, rather than making a decision unilaterally and then expecting South Korea to follow it," said Roh, who begins a five-year term in February.
Roh supports outgoing President Kim Dae-jung's "sunshine" policy of engaging North Korea. They believe dialogue is the only viable way to resolve the North's nuclear issue peacefully.
A top South Korean diplomat met with Chinese Foreign Ministry officials in Beijing on Thursday to discuss North Korea's nuclear program, bringing together two major regional players in a bid to defuse tensions on the Korean peninsula.
South Korean Assistant Foreign Minister Lee Tae-sik conferred with Chinese Vice Foreign Minister Wang Yi on Thursday. South Korean officials confirmed that the North Korean nuclear issue was the main agenda item.
Some South Koreans worry that the nuclear dispute could trigger armed conflict on the Korean Peninsula, the world's last Cold War frontier. More than 2 million troops are massed on both sides of the Korean border, while about 37,000 U.S. troops are stationed in South Korea.
North of the DMZ, as the population starves and the isolated government threatens to restart its nuclear-weapons program, Pyongyang's latest pronouncements have seemed to regard American invasion — and victory over the invaders — as almost inevitable.
The reality is that North Korea is impoverished and dependent on outside food aid, much of it supplied by the United States via the U.N. World Food Program.
In the past two days, both Roh and Kim have expressed concern that Washington might impose heavy economic pressure on Pyongyang to give up its nuclear ambitions, and this could backfire and harden the North's stance.
U.S. State Department spokesman Philip T. Reeker said, "I don't think anybody has suggested at this point imposing sanctions."
Anti-U.S. sentiment was evident on the streets of Seoul on New Year's Eve, when about 22,000 South Koreans gathered near the U.S. Embassy to protest the deaths of the two teenage girls, who wre accidentally killed in June by a U.S. military vehicle.
Two U.S. soldiers whose vehicle killed the girls were cleared of negligent homicide charges in U.S. military courts last month.
Some protesters shouted for an end to the U.S. military presence in South Korea.
Tensions over North Korea's nuclear ambitions intensified Tuesday when Pyongyang expelled two U.N. inspectors monitoring its nuclear facilities and signaled it might pull out of the global nuclear nonproliferation treaty.
North Korea's ambassador to Moscow, Pak Ui Chun, told Russian news media Tuesday that his country intends to free itself from its last legal obligations under the international nuclear nonproliferation treaty, which seeks to confine nuclear weapons to the United States, Russia, Britain, France and China.
India and Pakistan also both have nuclear weapons, and Israel is believed to possess them as well.
In recent weeks, North Korea removed monitoring seals and cameras from nuclear facilities at Yongbyon that were frozen under a 1994 deal with the United States.
It says it is willing to resolve concerns over its nuclear program if the United States signs a nonaggression treaty, but Washington rules out any talks before the North changes course.
Fox News' Amy C. Sims, Marie-France Han, Paul Wagenseil and The Associated Press contributed to this report.