MIAMI, May 3 (Reuters) - David Beckham’s dream of building a futuristic waterfront stadium in Miami that would house his own professional soccer team has turned into a “not in my backyard” clash, pitting the retired English superstar against one of the world’s top cruise lines.

Royal Caribbean Cruises is at the forefront of efforts to block Beckham’s plans to build a 25,000 seat open-air stadium next to the port of Miami.

The cruise line is spearheading a group called the Miami Seaport Alliance, which has paid for full-page newspaper ads and TV and radio spots opposing Beckham’s plans. The alliance says a stadium would threaten the 200,000 jobs generated by the port, which is owned and operated by Miami-Dade County.

The port, built on a landfill island close to downtown, calls itself the “cruise capital of the world,” handling more than 4 million passengers in 2013. Formally known as PortMiami, it is also a large cargo container facility.

“A soccer stadium at PortMiami is downright nutty,” according to one ad by the alliance. “We cannot jeopardize well-paying jobs, like crane operators, longshore workers, and mechanics, for low-paying stadium jobs, such as concession sales,” it adds.

Royal Caribbean said in a statement on Friday a stadium would be a “poor use of (Miami’s) only port,” arguing it would disrupt cargo and cruise operations by adding at least 6,000 cars and 30,000 people to the downtown area.

John Fox, president of the Miami Seaport Alliance, who until recently headed government relations for Royal Caribbean in Washington, accused Beckham of a “land grab” this week, saying he suspected the stadium was a shoehorn for a much larger development plan on real estate close to the port entrance.

“We just don’t think they (Beckham’s group) are being honest with this community,” Fox said on Wednesday during a public debate in which he questioned how Beckham’s team could make money from soccer alone with only 25 scheduled games a year.

WATERFRONT SETTING

Beckham’s group, Beckham Miami United, insists the stadium must be located in a waterfront downtown setting, likening it to other franchises in Seattle, Portland, San Francisco, Baltimore and Pittsburgh. Neisen Kasdin, a land use attorney with the Akerman law firm who represents Beckham’s group, called the alliance’s attacks “false and misleading.”

The proposed stadium site is on land already slated for commercial development by the port’s own master plan, he said. Located half a mile (about 1 km) from the port entrance, the stadium would cause no problem for cruise ship or freight cargo operations, Kasdin added, noting games would be played mostly on Saturday evenings.

“It’s not a place you want to have out in the suburbs,” said Kasdin. “It’s great for the downtown life of a city.”

The port is currently undergoing $2 billion in capital improvements including deepening its main channel and construction of a port tunnel and rail link, allowing it to handle a new generation of larger container vessels set to begin using the expanded Panama Canal in 2016.

While the Seaport Alliance says it is supported by an array of local business groups and mayors, some of its supposed backers told Reuters the alliance misrepresented their position.

An attorney representing two chapters of the International Longshoreman’s Association in Miami said his members were “neutral” on the stadium proposal, contradicting statements by the Seaport Alliance.

The influential Miami Association of Realtors and the Florida Customs Brokers and Forwarders Association, also said they have yet to take sides, despite being named by Fox as backers of the alliance.

Other key players have remained silent, including the two other major cruise lines at the port, Carnival Cruise Lines and Norwegian Cruise Line.

MIAMI BEACH MAYOR IS WITH OPPONENTS

The mayor of Miami Beach, located near the port, has joined those opposed to a stadium near the port. Mayor Philip Levine is chief executive of Royal Media Partners, a media company that handles all publications for Royal Caribbean and its subsidiaries.

Levine told Reuters he saw no conflict of interest in his stand. “We love soccer, but this is all about traffic,” he said, adding the planned site would cause “horrible” congestion on a major causeway that links downtown Miami to the popular tourist hotel district in the southern part of Miami Beach.

Miami-Dade County Mayor Carlos Gimenez, in an opinion piece in the Miami Herald on Friday, urged both sides to temper their remarks, saying it was premature to judge the issue until county officials review the stadium impact, including a traffic study.

“We will not jeopardize any of the jobs our port provides,” he wrote.

Ultimately, the decision will rest with Miami-Dade County commissioners, although no timetable has been set for a vote.

Beckham along with his partners Simon Fuller, the founder of American Idol, and Bolivian-born cellular phone services company billionaire Marcelo Claure, unveiled plans in March to build the $250 million privately-financed stadium on land leased from the county. The plan includes shopping plazas, offices and hotels on the island port with sweeping views of downtown Miami.

Claure accused the Seaport Alliance of poisoning the stadium debate. “I am personally saddened that they have chosen to substitute constructive dialogue with attack ads.”

He accused Royal Caribbean of being selfish and said the selected site was currently under-used as it serves mainly as a car park for cruise line employees. If an independent traffic study showed the port stadium could disrupt cruise and freight operations, Beckham’s group would look at other sites, he said.

“Our goal is not to create chaos, but to create happiness,” Claure said.

The sport’s controlling body in the United States, Major League Soccer, is supporting Beckham’s bid to form a team in Miami, but has yet to award the franchise. MLS has made a downtown stadium location a condition of any deal.