ST. LOUIS — The widest drought to grip the United States in decades is getting worse with no signs of abating, a new report warned Thursday, as state officials urged conservation and more ranchers considered selling cattle.

The drought covering two-thirds of the continental United States had been considered relatively shallow, the product of months without rain, rather than years. But Thursday’s report showed its intensity is rapidly increasing, with 20 percent of the nation in the two worst stages of drought — up 7 percent from last week.

The US Drought Monitor classifies drought in various stages, from moderate to severe, extreme and, ultimately, exceptional. Five states — Colorado, Iowa, Kansas, Missouri, and Nebraska — are blanketed by a drought that is severe or worse. States such as Arkansas and Oklahoma are nearly as bad, with most areas covered in a severe drought and large portions in extreme or exceptional drought.

Other states are seeing conditions rapidly worsen. Illinois — a key producer of corn and soybeans — saw its percentage of land in extreme or exceptional drought balloon from just 8 percent last week to roughly 71 percent as of Thursday, the Drought Monitor reported.

Little rain and more intense heat is forecast for the rest of the summer.

‘‘Some of these areas that are picking up a shower here and there, but it’s not really improving anything because the heat has been so persistent in recent weeks, the damage already is done,’’ said Brian Fuchs, a climatologist at the National Drought Mitigation Center at the University of Nebraska in Lincoln.

‘‘Realistically, the forecast going forward is a continuation of warm, dry conditions through the end of August easily, and we may see them in the fall.’’

The drought stretches from Ohio to California and runs from Texas north to the Dakotas. Only in the 1930s and the 1950s has a drought covered more of the United States, according to National Climatic Data Center in Asheville, N.C.