The Trump administration on Thursday, pressing the president’s complaints about homelessness in California, demanded the state improve the way it deals with human waste, arsenic and lead in water as it escalated the administration’s war with the country’s most populous state.

In a letter to Gov. Gavin C. Newsom of California, Andrew Wheeler, the administrator of the Environmental Protection Agency, accused the state of “deficiencies that have led to significant public health concerns” and issued a veiled threat that federal funding to the state could be at risk.