WASHINGTON -- The head of a Pentagon agency apologized Thursday for saying a 700-ton explosion set for June 2 at the Nevada Test Site would send a "mushroom cloud over Las Vegas."

James Tegnelia, chief of the Defense Threat Reduction Agency, described his March 30 remarks to reporters as "unfortunate."

"I absolutely regret using the words I used last week," Tegnelia said in an interview after meeting Thursday with Rep. Shelley Berkley, D-Nev., in her office.

To many Nevadans, the mushroom cloud is a haunting icon that has come to symbolize the government's disregard for the health and safety of citizens during Cold War atmospheric nuclear testing.

Later in the day, Tegnelia met with Sen. Harry Reid, D-Nev., the Senate's minority leader, in a further attempt to smooth over the strong reaction to his remarks about the upcoming experiment.

Reid said after the meeting he was satisfied with the official's explanation.

"I now feel comfortable that (the agency) is taking all necessary precautions to make sure the test is done safely," he said.

"It seems to be well-planned, and all the necessary environmental tests and safety precautions are being done," Reid said. "At this point, there is no reason for the test not to go forward."

Government officials say the objective of the June 2 experiment, called "Divine Strake," is to collect data for the development of a conventional weapon that can destroy underground bunkers where enemies might store weapons of mass destruction.

"What we're trying to do is develop conventional weapons that could help reduce this requirement to use nuclear weapons to destroy these facilities," Teneglia said.

Tegnelia said the blast will create a dust cloud similar to those resulting from nuclear explosions.

The plume may reach 10,000 feet. But Tegnelia said the cloud should stay over the test site and is not expected to drift over Las Vegas or be visible from Las Vegas, according to his agency's current estimates.

"It has nothing to do with nuclear weapons," Tegnelia said. "It just has to do with the heat of the explosion -- the release associated with an explosion of that size."

The experiment will include the detonation of 700 tons of ammonium nitrate fuel oil solution in a 30-foot pit dug above one of the test site's tunnels about 90 miles northwest of Las Vegas.

The test will assess the capability of computer codes to predict the ground-shock environment and associated tunnel response to the blast. Contamination is unlikely because the tunnel has not been used in previous nuclear tests.

The media will be allowed to witness the test, according to agency spokeswoman Irene Smith.

Tegnelia emphasized the test poses no danger to the citizens of Nevada, and there are no plans to cancel it.

Although she said the 30-minute meeting went well, Berkley stopped short of saying she was reassured after talking to Tegnelia.

"I will have a more thorough answer for you, a more definitive answer after we've had an opportunity to review the NEPA (National Environmental Policy Act) environmental impact study (on the test) that is online," Berkley said.

Meanwhile, the Western Shoshone Indians called for a halt to the test, which they contended would take place on tribal lands the Indians are trying to reclaim.