Companies from Cuba's long-term trading partners such as Japan have stepped up interest in the Communist-ruled island since its detente with Washington, seeking to win investment projects before their U.S. competitors turn up.

"We are trying to find new business opportunities to establish some infrastructure projects ... as well as new trading opportunities," Mitsuyuki Takada, Senior Vice President of Mitsubishi Corp Global Strategy, told Reuters on the sidelines of the launch of the firm's new Havana office.

Local authorities had shown Takada and other visiting Mitsubishi executives around the Chinese-style special development zone at Mariel Bay earlier on Friday.

Cuba launched the zone, centered around a new container terminal, two-and-a-half years ago in a bid to become a shipment hub and spur new industrial projects. It offered investors significant tax and customs breaks.

Takada said the island had a strategic location at the center of the Caribbean and close to the United States, and stood to benefit from increased traffic through the renovated Panama Canal.

"From a logistics point of view, the Caribbean market has a big potential to grow," he said.

Mariel is part of a broader government drive in recent years to attract more investment to Cuba to spur economic growth.

Many foreign companies had previously been put off by its legal regime, the disadvantages associated with the U.S. economic embargo and restrictive labor policies.

But Cuba two years ago passed a new law offering investors steep tax cuts and promising a climate of investment security.

Shuichi Ijiri, who will head Mitsubishi Corp's new Havana office, said since "Cuba is changing" the company had decided to return at this time.

Ijiri said his company had a long trading relationship with Cuba, importing coffee beans to Japan and other Asian markets.

The Japanese government might help finance Mitsubishi Corp infrastructure projects in Cuba, Takada said. Japan is among the countries seeking to convince Cuba to sign investment contracts with its companies in return for writing off debt.

Cuba's First Vice President Miguel Diaz-Canel visited Tokyo last month for discussions there on debt, investment and trade.

While U.S. President Barack Obama has taken steps to hollow out the embargo on Cuba with executive orders, the lack of U.S. financing is hampering U.S.-Cuban business opportunities, experts say.

(Editing by Ed Davies)

By Sarah Marsh