With the stock market reeling as worries of a potential trade war cast a pall over Wall Street, President Donald Trump tried to soothe investor fears by suggesting the tariffs on steel and aluminum announced Thursday would help America be great again.

Within a series of tweets early Friday, Trump tried to sway investor opinion by saying, “trade wars are good, and easy to win.”

Steel and aluminum industry groups were happy. The American Iron and Steel Institute said it was “pleased” with the tariffs announcement, while the Aluminum Association said “we appreciate” the president’s commitment to help the aluminum industry.

But investors didn’t seem to buy it, as the Dow Jones Industrial Average DJIA, -2.75% tumbled as much as 391 points early Friday, before paring losses to close down 71 points. That follows the 420-point drubbing the Dow took after the tariffs were announced. See Market Snapshot.

Don’t miss: Here’s why the stock market is taking the Trump tariffs so hard.

Also read: Opinion: Tariffs on steel, aluminum are long overdue.

In an effort to find the answer to whether trade wars are good or bad for the Dow, MarketWatch asked the current 30 companies that make up the index their thoughts on recent events. A number of companies responded by referring MarketWatch to industry/trade group statements, or a research note.

Pay particular attention to the stand taken by the Business Roundtable, an association of chief executive officers of leading American companies, that has the CEOs of 22 Dow companies as members.

Here’s how companies responded (or didn’t respond):

Coca-Cola Co. KO, -3.26% referred MarketWatch to a statement attributed to Can Manufacturers Institute (CMI) President Robert Budway, in which he said tariff restrictions will have “severe economic impact” on the can manufacturing industry and its employees, as well as consumers of aluminum cans. (Coke is not a CMI member company, but CEO James Quincey is a member of the Business Roundtable.)

“Like most industries, can makers depend on predictability in supply and price. If the aluminum supply is hindered by unnecessary tariffs, it could lead to supply inefficacies and affect product availability,” Budway said.

“We are extremely disappointed that the president did not side with American consumers and workers. CMI plans to file a petition with the Commerce Department asking for administrative relief from tariffs on imports of aluminum can sheets, aluminum ingots and steel tinplate,” Budway added.

Don’t miss: Trump’s tariffs will hurt the 6.5 million U.S. workers at steel-consuming manufacturers.

Exxon Mobil Corp. XOM, -3.21% referred MarketWatch to a number of industry groups, including the American Petroleum Institute (API) and Business Roundtable. (Exxon Mobil is a member of both industry groups.)

API said it “supports free trade,” particularly in the oil and natural gas industries, but in other industries as well.

“Global trade and investment regimes are of critical importance. Free trade provides opportunities for business growth and expansion; increases the range of oil, natural gas, and other petroleum products available to consumers; enhances market-based production globally; and contributes to global energy cooperation,” the statement said.

“In addition, API opposes policy measures under Section 232 - such as new tariffs quotas or other measures to restrict U.S. imports of steel and aluminum—that would be based on a broader definition of ‘national security.’”

Goldman Sachs Group Inc. GS, -1.41% responded by sending MarketWatch a research note dated March 1 that was sent to clients before the then-anticipated Trump announcement was made. (CEO Lloyd Blankfein is not a member of the Business Roundtable.)

“This is likely to escalate trade tensions, particularly as it looks likely to apply to a broad group of countries including to some allies of the U.S.e expect further disruptive trade developments over the coming months, including stalled NAFTA [North American Free Trade Agreement] negotiations and potential restrictions on Chinese trade and investment,” wrote Goldman chief economist Jan Hatzius.

“There is a good chance that this could eventually lead the president to announce he intends to withdraw from NAFTA, but such an announcement does not appear likely in the near term, in our view,” he wrote. Read more about the Goldman note.

See also: Opinion: Look beyond the threat of steel tariffs to the 1.8 million jobs that could vanish if Nafta goes.

J.P. Morgan Chase & Co. JPM, -4.46% referred MarketWatch to a statement attributed to Joshua Bolten, chief executive of the Business Roundtable, of which J.P. Morgan Chase Chief Executive Jamie Dimon is a member.

The industry group said that while it “shares” the Trump’s goal of addressing overcapacity of steel and aluminum, it urges Trump to pursue “other approaches” that won’t put the economy at high risk.

“Business Roundtable strongly disagrees with [Thursday’s tariff] announcement because it will hurt the U.S. economy and American companies, workers and consumers by raising prices and resulting in foreign retaliation against U.S. exporters,” the statement said. “Using ‘national security’ tools to implement tariffs could embolden other countries to impose ‘national security’ tariffs on U.S. exporters or otherwise restrict U.S. goods and services sold to their markets.”

Walmart Inc. WMT, +0.56% referred MarketWatch to comments made by the Retail Industry Leaders Association, or RILA. (Walmart CEO Doug McMillon is a member of the Business Roundtable.)

“Today’s announcement that the Trump administration intends to unilaterally impose tariffs on steel and aluminum imports could have severely negative consequences for the American economy. If broadly applied, these tariffs will have a downstream impact on every sector, and will raise the stakes for other countries to take retaliatory measures that will hurt America’s exporters,” Hun Quach, RILA vice president of international trade said in a statement.

While Quach acknowledged Trump’s desire to challenge other countries’ trade violations, a broadly applied tariff could spark a potential trade war “that zaps consumer spending and American exports.”

Apple Inc. AAPL, +0.19% : No comment, but Apple CEO Tim Cook is a member of the Business Roundtable.

Caterpillar Inc. CAT, -5.36% : No comment, but Jim Umpleby is a member of the Business Roundtable.

Microsoft Corp. MSFT, -0.21% : No comment. CEO Satya Nadella is not a member of the Business Roundtable.

United Technologies Corp. US:UTX declined to comment. CEO Gregory Hayes is a member of the Business Roundtable.

Visa Inc. V, -3.02% declined to comment, but CEO Alfred Kelly Jr. is a member of the Business Roundtable.

How we got here: A history of U.S. steel wars before Trump

Companies that had not responded to MarketWatch requests for comment on the matter (most of whose CEOs are members of the Business Roundtable):

3M Co. MMM, -5.67% CEO Inge Thulin is a member of the Business Roundtable.

American Express Co. AXP, -5.73% CEO Kenneth Chenault is a member of the Business Roundtable.

Boeing Co. BA, -2.68% CEO Dennis Muilenburg is a member of the Business Roundtable.

Chevron Corp. CVX, -3.84% CEO Mike Wirth is a member of the Business Roundtable.

Cisco Systems Inc. CSCO, -2.27% CEO Chuck Robbins is a member of the Business Roundtable.

DowDuPont Inc. US:DWDP DuPont CEO Edward Breen is a member of the Business Roundtable.

General Electric Co. GE, -9.01% CEO John Flannery is a member of the Business Roundtable.

Home Depot Inc. HD, -2.24% CEO Craig Menear is a member of the Business Roundtable.

Intel Corp. INTC, -0.83% CEO Brian Krzanich is not a member of the Business Roundtable.

International Business Machines Corp. IBM, -2.77% CEO Virginia Rometty is a member of the Business Roundtable.

Johnson & Johnson JNJ, -3.83% CEO Alex Gorsky is a member of the Business Roundtable.

McDonald’s Corp. MCD, -2.32% CEO Stephen Easterbrook is not a member of the Business Roundtable.

Merck & Co. MRK, -4.10% CEO Kenneth Frazier is not a member of the Business Roundtable.

Nike Inc. NKE, -1.50% CEO Mark Parker is not a member of the Business Roundtable.

Pfizer Inc. PFE, -2.90% CEO Ian Read is a member of the Business Roundtable.

Procter & Gamble Co. PG, -1.33% CEO David Taylor is a member of the Business Roundtable.

Travelers Companies Inc. TRV, -3.40% CEO Alan Schnitzer is a member of the Business Roundtable.

UnitedHealth Group Inc. UNH, -3.84% CEO David Wichmann is not a member of the Business Roundtable.

Verizon Communications Inc. VZ, -1.96% CEO Lowell McAdam is a member of the Business Roundtable.