(CNN) Agriculture Secretary Sonny Perdue said Thursday he is concerned about the idea that the Trump administration would close the US-Mexico border -- a threat President Donald Trump floated and then later backed off on -- which Perdue warned would have been "detrimental" to trade.

"I don't see any threat right now to close the border," he said at a Senate Appropriations Subcommittee hearing Thursday. "We've advocated I think as well as others how detrimental this would be to US commerce."

Perdue was asked by Sen. Tammy Baldwin, a Wisconsin Democrat, about fears from her state's dairy producers, which include retaliatory tariffs from Mexico targeting cheese and other US agricultural products.

"Even with passing comments about closing down ports of entry has got Wisconsin farmers and cheese makers extremely concerned," she told Perdue.

The threat from President Donald Trump played out both in public and private over the last month. The President repeatedly warned he'd have the border closed if Mexico did not step up anti-drug trade efforts. Behind the scenes, he ordered officials to close the El Paso port of entry, followed by other ports, replying with indifference to their concerns about the trade impacts of such a move.

Read More