Seventy-four cities, 65 counties and four tribal areas in Nebraska declared states of emergency Tuesday as swaths of the Midwest battled rivers swollen by days of heavy rains and spring snowmelt.

Three deaths have been blamed on the flooding in Nebraska. As of Tuesday afternoon, more than 7 million people in 14 states live where a flood warning was still in effect, the National Weather Service said.

In Nebraska alone, the farm and ranch losses because of floods could reach $1 billion, the state's farm bureau said.

Vice President Mike Pence surveyed damage in Nebraska on Tuesday, talking to first responders and visiting a temporary shelter. He promised expedited action on presidential disaster declarations for Nebraska and Iowa.

“We’re going to make sure that federal resources are there for you,” Pence told volunteers at Waterloo, a town of less than 1,000 residents about 20 miles west of Omaha that was virtually cut off by the floodwaters.

About 200 miles of levees were compromised in Nebraska, Iowa, Missouri and Kansas, the U.S. Army Corps of Engineers said. Thousands of people have been driven from their homes by the fast-rising waters.

Flooding is expected to continue throughout the week in several states as high water flows down the Missouri River.

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“The levees are busted, and we aren’t even into the wet season when the rivers run high,” said Tom Bullock, the emergency management director for Missouri’s Holt County.

In North Dakota, Fargo Mayor Tim Mahoney declared a state of emergency despite what he described as tremendous strides in permanent flood protection in recent years.

“This is a very serious flood forecast, and we will meet it with a serious response," he said. "It is critically important for everyone to know that we will need the public’s assistance. We cannot be complacent."

In Illinois, Freeport City Manager Lowell Crow said the town of 25,000 residents west of Rockford could see an all-time record flood along the Pecatonica River, which was at its highest level since 1933 on Tuesday. City officials braced for flooding in the downtown area, he said.

In Missouri, 130 people were urged to leave their Atchison County homes near strained levees, three of which had been overtopped by water. Missouri State Highway Patrol crews were on standby for rescues.

“The next four to five days are going to be pretty rough,” said Rhonda Wiley, the county emergency management and 911 director.

The Missouri River was expected to crest Thursday in St. Joseph, Missouri, at its third-highest level on record, the National Weather Service said. Military C-130 planes have been evacuated from nearby Rosecrans Air National Guard Base.

In Iowa, water stood 10 feet high near Pacific Junction, where only the top halves of gas stations, homes and storage units were visible. Mills County Emergency Management Director Larry Hurst said the flooding might be worse than some of the most extreme historical events – in 1952, 1993 and 2011.

"This is actually different even than the flood of '52," he said. "There's water on this entire basin."

Touring the damage, Reynolds said the flooding was unlike anything she had seen before as the state's top elected official.

“It looked like an ocean,” she said.

Water gushed through a levee break near the Plattsmouth Toll Bridge, where the Platte and Missouri Rivers converge. The mystery, Hurst said, is how long it will take for the water to recede.

"To tell you the truth, I don't know," he said. "I don't think anybody knows."

Glenwood Mayor Ron Kohn said his city of 5,000 was in pretty good shape, but to the west, where the aging levee broke under rapidly rising waters last week, farms were swamped.

"That's all going to be gone until next year," Kohn said. "Rice is about all they could grow out there now."

Reynolds said 41 Iowa counties have requested and been approved for help through the governor's disaster proclamation last week. President Donald Trump tweeted his support for Reynolds and authorities who were fighting the floods.

In Nebraska, the National Guard said its members joined with the State Patrol to escort a caravan of semis and fuel tankers packed with food and supplies from Omaha to Fremont. The Department of Transportation cleared the way by "plowing over 5 inches of mud outside of Fremont," the National Guard said on Twitter. Nearly 70 percent of the state is under a disaster declaration.

Offutt Air Force Base

Offutt Air Force Base, home of the 55th Wing – the "Fightin' Fifty-Fifth" – was essentially underwater. Officials and airmen will not be able to get into roughly 60 structures until water recedes, and only mission-essential personnel are working at the installation, base spokesman Ryan Hansen said

"I am foremost grateful there have been no injuries reported by our Airmen or their families, proud of the effort by our Airmen & the community there to take care of one another & confident in our ability to continue generating combat airpower as @Offutt_AFB recovers," Air Force Chief of Staff Gen. David Goldfein tweeted.

Contributing: Shelby Fleig and Austin Cannon, Des Moines Register; Kristin Lam, USA TODAY; The Associated Press