South Korea's environment ministry is reviewing ways to talk with US forces about soil and water contamination on their army bases here, but to an extent that it won't affect the alliance of the two countries, its vice minister has said.

"(The ministry) has a particular concern over the contamination and purification process at US army bases and we're seriously considering ways to discuss the issue with our ally for a solution," Vice Environment Minister Ahn Byung-ok said at a press briefing on Tuesday.

"We'll do this within the boundary of not undermining the Korea-US alliance," Ahn said. 

Concerns have grown on possible environment damage on US bases in South Korea, including the largest one in Yongsan, central Seoul. A water survey by the Seoul city government showed an extremely high contamination of benzene, 587 times the permissible level.

Activists have blasted the Seoul government for its lukewarm stance over the issue, urging the environment ministry to release the rest of the results of the joint environmental surveys conducted with the US Forces Korea.

The ministry has revealed part of the reports and refused to make the full disclosure citing the South Korea-US Status of Forces Agreement.

Ahn accepted the criticism that the government needs to be clearer about whether it will fully disclose the reports.

"Nothing is in process right now, but we see the need to reach a consensus and tell the US army what we need," he said. "We'll deal with (the matter) with much caution because we're more than aware of the concerns stemming from North Korea's latest nuclear threat."

The US forces are relocating the bulk of their troops to Pyeongtaek on the outskirts of the capital. (Yonhap)