WASHINGTON — The Environmental Protection Agency sharply criticized the State Department’s impact statement for the proposed Keystone XL oil pipeline, saying the report failed to adequately consider the climate change impacts of building the pipeline or to realistically assess alternative pipeline routes or modes of transport.

In a relatively unusual public squabble between agencies, a top E.P.A. official said in a letter to State Department officials that the department’s latest environmental statement for the 1,700-mile pipeline provided “insufficient information” to adequately judge the project, and that the E.P.A. could not sign off on the pipeline unless more complete studies were performed.

The letter was one of more than a million documents submitted as part of the public comment phase of the project. At the end of February, the State Department issued an environmental-impact statement for the pipeline, saying there was no conclusive environmental or economic reason not to build the project. The pipeline would carry a heavy form of oil known as bitumen from oil sands formations in Alberta to refineries in Texas.

Secretary of State John Kerry is expected to make a recommendation to President Obama on the pipeline later this year. The State Department must determine whether the project is in the national interest because it crosses an international border.