Secretary of Commerce Wilbur Ross straightens his papers during a Senate Finance Committee hearing on tariffs, on Capitol Hill, Wednesday, June 20, 2018 in Washington.

Senate Republicans and Democrats both criticized Commerce Secretary Wilbur Ross on Wednesday over what they called a confusing and damaging Trump administration process of imposing tariffs.

Appearing before the Senate Finance Committee, Ross defended the White House's measures targeting steel and aluminum imports due to what it deems national security concerns. In a rare move, the policy has united most lawmakers against the president,

On Wednesday, senators from both parties drilled into Ross over the tariffs on metals and separate actions targeting Chinese imports. Lawmakers broadly questioned the administration's trade actions, which have prompted retaliation from major trading partners such as China, the European Union and Canada.

Many raised concerns about costs passed on to manufacturers and consumers by higher-priced metals.

"These tariffs do not support U.S. national security," Finance Committee Chairman Sen. Orrin Hatch, R-Utah, said of the metals tariffs. "Instead, they harm American manufacturers, damage our economy, hurt American consumers and disrupt our relationship with long-term allies while giving China a free pass."

Sen. John Thune, a South Dakota Republican, focused on potential damage to the agricultural industry from retaliatory Chinese tariffs on American crops. The third-ranking GOP senator said the conflict with China "seems to be escalating out of control fairly quickly" as the world's two largest economies announce a series of broadsides.

"I'm increasingly concerned that the tariffs, both those in place and those that have been proposed, are going to hurt American consumers and our domestic businesses, especially in the agricultural sector, far more than they're going to persuade the Chinese to change their unfair trade practices," Thune said.

The hearing comes as duties imposed by Washington and Beijing have raised fears about potential economic harm and contributed to stock markets broadly falling early this week. The actions have strained relations between President Donald Trump and world leaders such as Canadian Prime Minister Justin Trudeau and French President Emmanuel Macron.

Ross defended the administration's actions, saying he believes they will deter allegedly unfair trade practices that Trump pledged to end. He also brushed off senators' concerns about a sloppy process of implementing the metals tariffs and hearing requests to exclude certain products from the measures. Lawmakers raised fears about the Commerce Department picking winners and losers in the U.S. economy.

"This administration is standing up for American families, American businesses and American workers by taking action to reduce imports that threaten our national security," the Commerce secretary said.

The White House also has made "no decision" on whether to recommend tariffs on automobiles and auto parts on national security grounds, Ross added. Several senators urged him not to impose the measures, arguing the actions would pass on even more costs to consumers.

Many senators said they agreed with the Trump administration's moves to crack down on alleged Chinese theft of intellectual property or modernize the North American Free Trade Agreement. However, several lawmakers questioned why steel from ally Canada is a national security threat.

Sen. Michael Bennet, D-Colo., repeatedly questioned what threat Canada posed. Ross said the administration did not "directly" or "individually" accuse Canada of imperiling Americans, but said it was part of a "global solution."

Sen. Pat Toomey, R-Pa., said he did not accept that justification. Toomey is one of the GOP senators advocating for legislation to limit the administration's ability to impose tariffs on a national security basis.

"I wish we would stop invoking national security because that's not what this is about. This is about economic nationalism and an economic policy of managing trade," the senator said.

Lawmakers on the panel repeatedly questioned the implementation of the tariffs. The committee's ranking member, Sen. Ron Wyden, D-Ore., said the moves "seem more like knee-jerk impulses than any kind of carefully thought out strategy."

"[The administration's] most obvious accomplishment on trade so far is sowing a lot of chaos that has united allies and China against us," the senator said.

Much of the criticism focused specifically on the flood of requests to exclude certain products from the steel and aluminum imports. Senators have called for a swifter resolution to the process and more transparency about what the administration is choosing to exclude and why.

Ross said Wednesday that the Commerce Department has issued determinations on 98 requests, granting 42 and denying 56. The Commerce secretary noted that "we'll be accelerating" the process.

An animated Sen. Claire McCaskill, D-Mo., who is up for re-election this year, accused Ross of picking "winners and losers" in a "chaotic and frankly incompetent" way.

Lawmakers also repeatedly asked if the Trump administration had started a trade war. He echoed the president in saying "we've been at a trade war forever."