U.N. inspectors visiting North Korea were given permission to visit the communist nation's key nuclear reactor for the first time in nearly five years, the head of the delegation said Wednesday, while the communist country reportedly test fired a short-range missile.

North Korea has allowed monitors from the U.N. nuclear watchdog to visit its Yongbyon nuclear facility on Thursday and Friday, International Atomic Energy Agency Deputy Director Olli Heinonen said.

"We are going to Yongbyon tomorrow," Heinonen told The Associated Press by telephone from Pyongyang.

• Monitor the nuclear showdown on the Korean Peninsula in FOXNews.com's North Korea Center.

He declined to comment on discussions with North Korean officials so far, but expressed satisfaction.

"The atmosphere is good," he said. "We held meetings today and expect to have more later today."

Heinonen, however, emphasized, that the trip to North Korea, which began Tuesday, is not an actual inspection.

"This is just a visit, not inspection," he said, adding that to begin the latter would require a formal agreement outlining how it would be conducted and which would be subject to approval by the IAEA board of governors.

North Korea agreed to close the plutonium-producing Yongbyon reactor in February in exchange for economic aid and political concessions. But the communist nation ignored an April deadline to do so because of a banking dispute with the United States.

That dispute has finally been resolved this week after months of delay, and Pyongyang announced Monday that it would move forward with the disarmament deal.

It would be the first time for U.N. nuclear inspectors to visit Yongbyon since North Korea expelled IAEA monitors in late 2002 after the current crisis broke out with U.S. accusations that Pyongyang had a secret, uranium-based weapons program.

Separately, North Korea appears to have test-fired a short-range missile Wednesday toward the waters off the Korean peninsula's east coast, South Korea's Yonhap news agency reported. The report said the firing is believed to be part of a routine training exercise

The Seoul government detected signs that the North launched the missile around 11:30 a.m. (0230 GMT), Yonhap news agency reported, citing an unidentified government official.

The facility is at the center of international efforts to stop North Korea's nuclear program. The country carried out its first atomic test explosion in October.

The negotiating climate has sparked optimism in North Korea's neighbors.

"After the consultation is over, I think it will be shut down as early as possible," South Korean Foreign Minister Song Min-soon said, referring to the North's reactor.

Song, leaving for Washington for talks with Secretary of State Condoleezza Rice, said the reactor's closure is now a "technical issue," which would not be subject to a "political decision" by North Korea.

Heinonen said Tuesday that the officials there who greeted his team at the airport in Pyongyang were friendly and appeared ready for discussions.

"It seems to be a good start," he told The Associated Press in a telephone interview.

He told the broadcaster APTN just after arriving in North Korea's capital that he would be "negotiating arrangements for verification of the shutdown and sealing" of the North's main reactor during the five-day trip through Saturday.

Separately, a delegation of European lawmakers who visited North Korea, told reporters Wednesday in South Korea that the North's government says it's committed to carrying out its promises on denuclearization.

"We had the real impression that they are willing immediately to shut down and they will start as they promised to do so," Hubert Pirker, who led the five-member European Union delegation to North Korea, told a news conference in Seoul.

Pirker, a member of the EU Parliament from Austria, also said Tuesday that North Korean officials were expecting "a totally new quality" in their relations with the United States.

He said that North Korea appeared to be getting over past mistrust of Washington.

North Korea has considered the U.S. its No. 1 enemy, accusing Washington of plotting to invade the communist nation. The two countries have been at odds since the 1950-53 Korean War, in which the U.S. fought on the side of South Korea.

Relations appear to have been improving since the U.S. helped release North Korean funds frozen in a Macau bank over allegations of money laundering and counterfeiting, enabling U.S. nuclear envoy Christopher Hill to make his first visit to Pyongyang earlier this month.

Hill said Saturday he believed the Yongbyon shutdown would happen within about three weeks.

In Manila, a top U.S. general said Wednesday that the U.S. military would help verify whether North Korea would shut down the Yongbyon reactor as promised and if it would try to move its operations elsewhere.

"We will try to verify the shutdown of Yongbyon in support of and in coordination with other agencies like the IAEA," U.S. Pacific Commander Timothy Keating told a news conference. "You bet, we're gonna pay very close attention."

Complete coverage is available in FOXNews.com's North Korea Center.