WASHINGTON — Senate Democrats, including Minnesota's Al Franken and Amy Klobuchar, dealt President Obama an embarrassing blow Tuesday, refusing to approve debate on one of his signature trade measures.

Obama had hoped to convince enough Democrats to join Republicans to begin discussions that will eventually lead to a vote on trade promotion authority. That authority allows the Senate and House a time-restricted up-or-down vote on free trade agreements, but no power to negotiate or amend the pacts.

Senate rules require a 60-vote majority to begin the debate on trade promotion, also known as fast track. It is seen as essential to completing two major trade agreements currently being negotiated by the White House. The 12-country Trans-Pacific Partnership is in its final stages. The 28-country Transatlantic Trade and Investment Partnership with the European Union is expected to conclude within the next few years. Together, the trade deals will include countries responsible for 60 percent of the world's economic output.

But neither will become law without fast track authority, most experts agree, because negotiators cannot make binding agreements.

Businesses throughout the U.S., including many of Minnesota's major corporate citizens, support the trade agreements that fast track legislation will produce. Cargill, General Mills, 3M, Medtronic and Target, among others, have ties to groups pushing for the legislation, saying it opens new markets to American businesses that would not otherwise exist.

At the same time, traditional Democratic constituencies, such as labor unions, human rights groups and environmentalists, oppose free trade agreements — worried about competitive disadvantages in pay, exploitation of children and forced labor in overseas markets, and a lack of regulatory oversight for pollution.

The fast track bill that was not approved for debate Tuesday had passed the Senate Finance Committee by a 20-6 bipartisan vote. But the whole Senate voted 52-45 along party lines with the exceptions of Delaware Democrat Tom Carper, who voted for debate, and Republican majority leader Mitch McConnell of Kentucky, who voted against debate as a parliamentary move that will help him if he needs to resurrect the legislation.

Obama to try again

The president's supporters said they will try again, and Obama summoned key Democrats to the White House to discuss possible strategies.

Tuesday's vote was a rebuke of the trade initiatives Obama has made a centerpiece of his second term. Even pro-trade Democrats who had indicated support abandoned Obama.

"Democratic presidents look at trade differently than Democratic members of Congress, Democratic activists and labor unions," said Norm Ornstein, an expert on congressional affairs at the American Enterprise Institute.

Part of it is scope. Nationally, free trade agreements can lead to net job gains. But in some individual states and communities the agreements inevitably cost jobs.

"Maybe those who voted against [trade promotion authority] view it as a political win, but we view it as a senseless economic loss," said Devry Boughner Vorwerk, Cargill vice president of corporate affairs. Trade promotion authority "is not an extraordinary grant of power; it's a necessity to maintain America's competitiveness in the global marketplace."

In an interview, Franken said he is "against fast track because we end up with an up-or-down vote and no ability to amend." Franken added that he and other Democrats want four trade measures that came out of the Senate Finance Committee considered simultaneously. That way the debate includes not only fast track, but also enforcement of labor standards in foreign countries, preferences for products from certain poor nations, controls on currency manipulation by foreign countries, and government-funded retraining of American workers who lose jobs because of free trade agreements.

Franken opposes the current form of the Trans-Pacific Partnership (TPP). "This is an area where I disagree with the president," he said.

Exports are at record levels in Minnesota, he said, but he is concerned that TPP will not increase employment. "The question," he said, "is what it does for American jobs."

Klobuchar was not available to comment, but a spokeswoman said in a statement that the senator "has been pushing for strong provisions to stop the illegal dumping of foreign steel that has had a major impact on workers on the Iron Range, as well as proposals dealing with foreign currency and other measures to help workers." Klobuchar voted not to allow debate on the fast track bill "because she continues to have concerns about whether the proposed legislation is strong enough for American workers."

Labor unions and other groups opposed to fast track say past free trade agreements lacked enforcement mechanisms and undermined U.S. workers. They point to job losses that occurred following passage of the North American Free Trade Agreement (NAFTA) 20 years ago.

Democrats vote no

Obama has countered with assurances that the Trans-Pacific Partnership and the Transatlantic Trade and Investment Partnership contain safeguards that NAFTA did not.

That was not enough to convince Senate Democrats.

Bill Clinton went through similar struggles with his Democratic partners when as president he secured passage of NAFTA, Ornstein said.

With the first attempt to get fast track to the Senate floor thwarted, supporters are looking for another way forward.

"We are discouraged that the Senate could not begin debate on legislation that would help the United States secure the strongest trade agreements that would benefit America's farmers, workers, and businesses," said David Thomas, president of the Trade Benefits America Coalition, whose members include 3M, Medtronic, General Mills and Target. "We hope the Senate will take up and pass this bill as soon as possible."

Simultaneously debating trade promotion authority, foreign working conditions, displaced U.S. worker retraining, preferential tariffs for poor nations, and currency manipulation will be hard because the issues involve separate pieces of legislation.

Whatever approach they take, Congress members ultimately face an unpleasant choice about giving up control, Ornstein added: "People say: 'I want to vote for a trade deal that works. But once we vote [for fast track] we lose the ability to filibuster.' "

The Associated Press contributed to this report.

Jim Spencer • 202-383-6123