Iran claimed Wednesday that a newly built U.N. station to detect nuclear explosions was set up near its border so that world powers could spy on the country, an accusation that underscored the growing bitterness in Tehran's relations with the West.

Construction was completed last week on the seismic monitoring station in neighboring Turkmenistan, a few miles from the Iranian border. It is one of roughly 275 such facilities operating around the world to detect seismic activity set off by blasts from nuclear tests _ such as ones in recent years by North Korea.

Iran protested the facility even though it asserts it is not trying to produce nuclear arms. Tehran has been resisting heavy pressure in recent months to sign on to a U.N.-backed plan aimed at thwarting any attempt to build atomic weapons.

Abolfazl Zohrehvand, an adviser to Iranian nuclear negotiator Saeed Jalili, said the international treaty that allows for setting up such observatories is an "espionage treaty."

"With the disclosure of the identity of such stations, it is clear the activity of one of them (in Turkmenistan) is to monitor Iran," Zohrehvand told state IRNA news agency.

The U.N. commission that seeks to ban all nuclear tests said the decision to build the station was made more than a decade ago with Iran's involvement. There are already three similar stations inside Iran itself _ in Tehran and the southern towns of Shushtar and Kerman, according to the commission.

The network of sensors monitors nuclear explosions worldwide, not in a specific country, said Annika Thunborg, a spokeswoman for the Vienna-based Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, or CTBTO. She said the new facility was unconnected to concerns over Iran's program.

"The building of the station has nothing to do with recent reports about Iran," Thunborg said. "Iran is a member state of the CTBTO, together with 181 other countries, and is party to the decisions made by the CTBTO."

The CTBTO announced last week on its Web site that the new nuclear warning station has been set up between Turkmenistan's Karakum Desert and the Kopet mountain range. It said the station has now been fully constructed and is currently undergoing testing.

But Iran's Zohrehvand said the CTBTO is a "security and espionage treaty, even more dangerous" than the Nuclear Non-Proliferation Treaty's additional protocol, which allows intrusive inspections of nuclear facilities in particular member states. Iran is a member of both the CTBTO and the NPT.

The U.S. and some of its allies suspect Iran's nuclear program is a cover to secretly develop nuclear weapons. Iran has denied it and said the program is geared toward generating electricity.