U.S. industries as diverse as aerospace, agriculture and apparel lauded a historic 12-nation Pacific trade deal struck Monday, while pharmaceutical makers, tobacco companies and others criticized the pact as falling short in key areas.

Completion of the Trans-Pacific Partnership, the biggest trade deal in a generation, marks a victory for President Barack Obama, who said it would open new markets to American products and set high standards for protecting workers and the environment.

The pact among the U.S., Japan, Australia, Vietnam and eight other countries around the Pacific—though not China—lowers trade barriers for goods and services ranging from poultry to building materials, and sets commercial rules for two-fifths of the global economy.

But the president now faces an arduous challenge of winning approval for the agreement in a divided Congress during a heated presidential campaign and amid upheaval in the Republican ranks.

The congressional debate could be influenced in part by diverting views from industry, as well as continued criticism of the pact from labor, consumer and environmental groups. Many U.S. industry groups on Monday said they were reserving final judgment until they had time to study the details.

Several prominent pro-trade Republicans—whose support could be vital to moving the trade agreement through Congress—offered chilly appraisals of the final product.

“While the details are still emerging, unfortunately I am afraid this deal appears to fall woefully short,” said Sen. Orrin Hatch of Utah, chairman of the Senate Finance Committee. Rep. Paul Ryan of Wisconsin, chairman of the House committee that oversees trade, said he had “concerns surrounding the most recent aspects of the agreement” and was “reserving judgment” until he could study the details.

A Ryan aide said the chairman’s concerns covered a spectrum of contentious issues in the deal, from dairy products to protections offered to drug makers and restrictions on the legal rights of big tobacco companies.

Within the business world, some of the broadest support came from the farm sector. The TPP would eliminate trade partners’ import taxes of as high as 40% on U.S. poultry products and fruit and 35% on soybeans, while seeking to minimize unpredictable export bans that can upend business for agricultural firms.

Cargill Inc., a giant grain exporter and meat processor, urged lawmakers to support the pact, saying it could set a new standard for international trade and help improve food security in developing countries.

Congress will have at least 90 days to review the deal, meaning it won’t come to a vote until January at the earliest—right as the 2016 presidential race begins in earnest.

Some top presidential candidates panned the pact. Republican front-runner Donald Trump said in a tweet that “TPP is a terrible deal.” Democratic candidate and Vermont Sen. Bernie Sanders called it “disastrous” and a victory for “Wall Street and other big corporations.”

Mr. Obama struggled earlier this year to win congressional passage of crucial legislation to move the TPP deal along, with the highest hurdle coming in the House, where just 28 Democrats approved of giving the president special powers to negotiate the accord.

The House is all but certain to pose the biggest challenge in winning final approval. On Monday, a number of liberal critics of the deal said it did little to protect vulnerable industries or promote job creation.

Some big U.S. manufacturers seconded those worries. Ford Motor Co. , which has been outspoken in its concern about stipulations preventing currency manipulation, urged Congress to reject the current deal. But Detroit auto makers don’t have as much to complain about as some had feared when Japan joined the talks. A senior administration official said U.S. tariffs that protect the domestic car industry won’t be eliminated for 25 years, with truck tariffs ended only after 30 years.

Other big industry groups were more positive. The National Association of Manufacturers applauded the pact, which the White House said would eliminate import duties of up to 59% on U.S. machinery shipped to TPP partners.

Boeing Co. , the largest U.S. exporter by value, said the deal would help it compete overseas, where it gets 70% of its commercial airplane revenue, while computer-chip giant Intel Corp. said it could bolster U.S. tech companies through “critical” intellectual property protections and encryption standards.

In apparel, the pact could enlarge foreign-market access while also helping U.S. giants like Nike Inc. ship goods home from overseas factories. The company said Monday the agreement “will allow us to innovate, expand our business and drive economic growth.”

Michael Penner, chief executive of Peds Legwear Inc., called TPP “a big deal.” For now, the company’s Hildebran, N.C., plant is producing socks almost entirely for North America, but he hopes the accord eventually will help him export to Japan and elsewhere.

Big drug companies’ main trade group, Pharmaceutical Research and Manufacturers of America or PhRMA, pointed to a provision that seems to protect biotech drugs from lower-priced competition for at least five years plus potentially more. The industry sought the 12 years of intellectual-property protection that biotech drugs receive in the U.S., and the duration was a sticking point until the end of the talks.

“While we await the final details, it appears that the ministers missed the opportunity to encourage innovation that will lead to more important, life-saving medicines that would improve patients’ lives,” PhRMA said in a statement.

Tobacco companies are among losers in the pact. The agreement is the one of the first in the world to allow countries to prevent the tobacco industry from suing foreign governments over antismoking measures in special arbitration panels.

Philip Morris International Inc. on Monday said the provision “undermines the core principle of equality.”

—Tripp Mickle and Theo Francis contributed to this article.