The US Environmental Protection Agency (EPA) has agreed to impose emissions standards for new gas and diesel engines that are used in a stationary capacity.

The rules will govern applications such as on-site electric generation, oil and gas development, and agricultural pumps and equipment.

Previously emissions from stationary engines had not been covered by the EPA's federal requirements, but were left instead to a mixture of state and local regulations.

Under the terms of the new strategy the EPA will propose emission standards for stationary diesel engines by the end of June next year, with final standards agreed upon by June 28th, 2006.

The decision should bring clarity to the issue, which had already been contested by some special interest groups.

Environmental Defense, one of the groups to bring such a case, estimates that there are about half a million diesel and gas stationary engines in use in the US.