The furor over the national security implications of a United Arab Emirates company acquiring a British company that operates six major U.S. ports is only one of a series of cross border mergers setting off alarm bells in the halls of governments around the globe.

Whether it's the national security trump card played so often in the post-9/11 world or fear of massive job losses in what are viewed as vital national industries, government officials have forcefully inserted themselves into global deal making.

"It's clearly something we can expect to see more of," says Ravi Madhavan, who teaches business strategy at the University of Pittsburgh's Katz Graduate School of Business. "I think it's a sign of how complex our world has become."

An $18.5 billion bid last summer for California oil producer Unocal by The China National Offshore Oil Corp., as well as a Chinese bid for troubled appliance maker Maytag, raised fears reminiscent of the 1980s, when cash-flushed Japanese investors went on a U.S. shopping spree. Both bids failed, but China's desire to become a global economic powerhouse and its large cash reserves mean Chinese investors will continue shopping for attractive overseas assets, Mr. Madhavan says.

More recently, Mittal Steel's hostile $23 billion bid for Arcelor Steel has raised concerns among French and Spanish officials. Meanwhile, the French government recently gave its approval for the merger of government-owned Gaz de France with Suez, a privately owned French utility subject to a takeover bid by an Italian rival.

"Mergers seem to be OK as long as it's the French company doing the acquiring," says Terrence Guay, who teaches international business at Penn State's Smeal College of business.

Still, the number of cross border mergers that ignite political or national concerns are in the distinct minority. Mr. Madhavan said there were about 5,100 cross border deals in 2004.

"If we think about how many made it to the headlines, it's a very small number," he says.

Those that do generally fall into several categories. The thought of Dubai Ports World acquiring Peninsular & Oriental Steam, the current manager of ports in Philadelphia and five other U.S. cities, is a natural opportunity for politicians to posture as stalwart defenders of national security.

Another issue that politicians do not want to be seen as soft on is jobs. Mergers frequently mean layoffs, usually at the company being acquired. That is one of the major concerns with Mittal's bid for Arcelor and why officials in Spain and France, where Arcelor has operations, are interested.

"That certainly creates a political constituency and a reason for the government to get involved," Mr. Madhavan says.

A related trump card convenient for politicians to play is sentiment in many corners against the increasingly global nature of the economy. The United States isn't the only country worried about losing jobs to China and other low-cost areas. It's also a concern in Western Europe, where companies are fleeing to lower-cost opportunities in Eastern Europe.

"It's a backlash against a lot of the globalization that people see," says Mr. Guay.

Patriotism makes cross border mergers in some industries -- including steel, defense and airlines -- more likely to spark government scrutiny.

"There is a sense in many of these deals that, in the country in which the target company is located, national pride gets in the way," says Robert Dammon, who teaches at Carnegie Mellon University's Tepper School of Business.

Much to the consternation of their neighbors in the European Union, the French have identified industries they consider to be vital to the nation's interests and are doing their best to protect them from foreign intruders. In 2004, the government arranged the merger of French drug maker Aventis with Sanofi-Synthelabo in order to thwart Swiss drug maker's Novartis' pursuit of Aventis.

"The French government has been particularly active in doing these kinds of things," Mr. Madhavan says.

A letter written last week by United Steelworkers of America President Leo Gerard to President Bush puts a U.S. face on concerns many governments have regarding cross border marriages. Mr. Gerard recommended a comprehensive review of the Committee on Foreign Investment in the United States, the group that approved the ports takeover.

In making the suggestion, he cited prior investments that, in his view, jeopardized national security, resulted in jobs moving overseas and the loss of critical technology.

To be sure, hard questions deserve to be asked about these transactions. However, some perspective is also in order.

Mr. Madhavan notes that political intervention in deal making tends to run in cycles. Two decades after a wave of massive Japanese investment in U.S. assets, "Japanese investments have become an accepted part of the economic scene."

"Today, I don't think a Japanese investment in the United States would raise many hackles," he says.

His comment is interesting in light of Toshiba's $5.4 billion purchase of Monroeville-based Westinghouse Electric Co., a nuclear powerhouse owned by British Nuclear Fuels PLC. The same committee that approved the ports deal must take a look at the Westinghouse transaction.