Speaking Sunday on CNN's "State of the Union," Ernst was asked by Dana Bash when she'll say "time's up" on Trump's negotiations with China, as retaliatory tariffs take their toll on the nation's farmers.
The Trump administration rolled out a second aid package for American farmers Thursday, worth $16 billion.
Trump said the aid will include $14.5 billion in direct payments to farmers through the market facilitation program. There will be three payment installments, beginning in July, while additional payments will follow in November and January as needed.
Another $1.4 billion will be allocated to the Food Purchase and Distribution Program to purchase surplus commodities affected by the trade war. Those goods will then be distributed to schools, food banks and other groups, the White House said.
Ernst said some farmers she's spoken with understand Trump's goals and wonder why previous presidents have not "stood up" for them.
She stressed that farmers in Iowa are in a "really difficult situation," but noted there are also national security concerns to be weighed when it comes to taking on China on trade.
"It’s hurting all over the country with the tariffs. But at the same time, we do have to get China to the table. We have to stop them from stealing intellectual property. We have to stop them from forced technology transfers. All of that is detrimental not only to our economy, but to our national security," she said.
At the same time, she called the situation "tenuous," doubting a deal will happen this summer.
"The president has called our farmers 'patriots.' It doesn’t pay the bills, but we will see in the upcoming months how long we can sustain."
Trump defended the tariffs earlier this month on Twitter, writing of the "great Patriot Farmers," who he claimed will benefit from his policies.
At a joint press conference in Japan Monday with Prime Minister Shinzo Abe, Trump said the U.S. is "not ready to make a deal" with China.
He added that "sometime in the future, China and the United States will absolutely have a great trade deal."
Democratic presidential front-runner Joe Biden blasted Trump earlier this month over the escalating trade war with China.
Biden said Trump has "gone about it all the wrong way," adding that "the only people paying the price are farmers and working people right now."