SEOUL — North Korea condemned a recent US pledge to provide nuclear defense of South Korea, saying Thursday that the move boosts its justification to have atomic bombs and invites a potential "fire shower of nuclear retaliation."

The commentary in Pyongyang's main Rodong Sinmun newspaper was the North's latest reaction to last week's summit between President Barack Obama and South Korean President Lee Myung-bak. The allies issued a joint statement committing the U.S. to defend the South with nuclear weapons.

South Korean children walk by North Korean mock Scud-B missile, back left, and other South Korean mock missiles at the Korea War Memorial Museum in Seoul, South Korea. (Photo: AP)

The North's newspaper claimed that the "nuclear umbrella" commitment made it more likely for the US to mount a nuclear attack on the communist North, and only "provides us with a stronger justification to have nuclear deterrent."

It also amounts to "asking for the calamitous situation of having a fire shower of nuclear retaliation all over South Korea" in case of a conflict, the paper said.

North Korea has long claimed that the US is plotting to invade it and has used the claim to justify its development of nuclear weapons. The US has repeatedly said it has no intention of attacking the North.

In a separate editorial marking the 1950 outbreak of the Korean War, the Rodong said the North "will never give up nuclear deterrent ... and will further strengthen it" as long as Washington remains hostile.

The war ended in 1952 with a truce, not a peace treaty, leaving the peninsula divided and in a state of war. The US has 28,500 troops in South Korea to protect against hostilities.

Ties between the two Koreas warmed significantly after the first-ever summit of their leaders in 2000, but relations soured after the conservative Lee took office last year.

The Rodong called Lee a "hound" of the US "master" in Thursday's commentary.

The new UN resolution seeks to clamp down on North Korea's trading of banned arms and weapons-related material by requiring UN member states to request inspections of ships carrying suspected cargo.

North Korea has said it would consider interception of its ships a declaration of war.

The US has been seeking to get key nations to enforce the sanctions aggressively. Secretary of State Hillary Rodham Clinton called the foreign ministers of Russia and China to discuss efforts to enforce the UN punishments, State Department spokesman Ian Kelly said.

The Kang Nam is believed to be the first North Korean ship to be tracked under the resolution. It left the North Korean port of Nampo a week ago and is believed bound for Burma, South Korean and US officials said.

Burma's state television on Wednesday evening said another North Korean vessel was expected to pick up a load of rice and that the government had no information about the Kang Nam.

A senior US defense official said Wednesday that the ship had already cleared the Taiwan Strait.

He said he didn't know how much range the Kang Nam has—whether or when it may need to stop in some port to refuel—but that the ship has in the past stopped in Hong Kong's port.

Another US defense official said he tended to doubt reports that the Kang Nam was carrying nuclear-related equipment, saying the information officials have received seems to indicate the cargo is conventional munitions.

The US officials spoke on condition of anonymity because they were discussing intelligence.

The US and its allies have not decided whether to contact and request inspection of the ship, Pentagon press secretary Geoff Morrell said Wednesday. He said he didn't believe a decision would come soon.

Reports about possible missile launches from the North highlighted the tension on the Korean peninsula.

The North has designated a no-sail zone off its east coast from June 25 to July 10 for military drills.

A senior South Korean government official said the ban is believed connected to North Korean plans to fire short- or mid-range missiles. He spoke on condition of anonymity, citing department policy.

South Korea's Yonhap news agency reported that the North may fire a Scud missile with a range of up to 310 miles (500 kilometers) or a short-range ground-to-ship missile with a range of 100 miles (160 kilometers) during the no-sail period.

US defense and counterproliferation officials in Washington said they also expected the North to launch short- to medium-range missiles. The officials spoke on condition of anonymity to discuss sensitive intelligence.

North Korea had warned previously it would fire a long-range missile as a response to UN Security Council condemnation of an April rocket launch seen as a cover for its ballistic missile technology.

Associated Press writers Hyung-jin Kim in Seoul and Pauline Jelinek, Pamela Hess and Lolita Baldor in Washington contributed to this report.