"Congress keeps putting off the big issues, like deficit reduction, and I don't think we have that luxury," said Thune, R-S.D. "We will be following in the footsteps of Greece if we don't do something."
Thune, who spoke to a group of about 50 residents in the Williams Library at Northern State University, said Greece, which has been on the brink of bankruptcy, has a debt-to-gross domestic product ratio of 160 percent. The United States has a debt to GDP ratio of 100 percent.
The U.S. should get back to a 60 to 70 percent ratio, he said.
"We need to act soon," he said.
The federal government spends 25 percent of all money in the country, which is up from the 21 percent average from the pre-Obama years, Thune said. That percentage continues to rise.
In order to rein in the deficit the country needs to reform entitlement programs such as Medicaid, Medicare and Social Security, three of the biggest areas of the federal budget, Thune said.
Citizens asked a variety of questions after Thune's opening remarks on the deficit.
Other topics and the senator's responses from Tuesday's Aberdeen gathering included:
• Energy — The country needs to get more serious about developing domestic sources of energy and pursue an "all of the above strategy" for developing energy sources such as gasoline, bio-fuels, nuclear, natural gas and renewables.
Not supporting the Keystone Pipeline is a missed opportunity, he said.
Gas prices, which are high and likely will rise this summer, might cause citizens to pressure Congress for more action.
• Tax policy — Thune supports lowering the overall tax rate and eliminating loopholes. He wants America to have a lower tax structure to encourage business development here.
• Regulation — There is too much government regulation, he said. He gave the example of a proposed Department of Labor Act, which would regulate what type of work children could do on family farms. The law showed a complete lack of understanding of how farm families operate and was an example of "over reaching" government, he said.
• Health and Human Services ruling on contraceptives — Thune said Republicans in the Senate will introduce a bill to repeal President Obama's policy on requiring religious health care organizations to provide health insurance coverage for contraceptive care. Even though President Obama has modified the policy somewhat, it still is a religious freedom issue and a reach of government issue, Thune said.
The bill will not get anywhere, because the president will veto it, he said.
• Iran — Thune said the world continues to be a dangerous place and that it is important to keep the military strong.
"The Iranian situation is really hot right now," he said. "If Iran gains a nuclear capability it will set off a chain reaction."
Thune said it is important to look at current threats as well as future threats.
"If you don't get national security right, the rest is just conversation," he said.
The meeting, which lasted 80 minutes, ended with Thune recognizing Bob Olson, Northern State University athletic director, who is retiring.
Thune praised Olson's career and said that one of his greatest accomplishments was achieving success while remaining a very nice guy.