The prototype will likely be able to fly in 2014, Lt. Gen. Hideyuki Yoshioka, director of air systems development at Japan's Ministry of Defense, said in an interview with The Associated Press.

He said Japan has put 39 billion yen ($473 million) into the project since 2009, after it became clear the United States was not likely to sell it the F-22 "Raptor" — America's most advanced fighter jet — because of a congressional export ban.

"We are two years into the project, and we are on schedule," Yoshioka said Monday.

Yoshioka stressed that a successful test flight of the prototype, dubbed "Shinshin," or "Spirit," does not mean Japan will immediately start producing stealth aircraft. The prototype is designed to test advanced technologies, and if it is successful the government will decide in 2016 how to proceed.

Japan is feeling the pressure of a regional dogfight over fighter superiority.

"If the countries surrounding Japan have stealth capabilities, Japan will need to develop those capabilities itself to ensure our own defense," said Col. Yoshikazu Takizawa of the Defense Ministry's Technical Research and Development Institute.

Japan relies to a large degree for its defense on its alliance with the United States, which has a significant number of fighters and other aircraft, along with some 50,000 troops, stationed around the Japanese archipelago.

But that alliance, and Japan's relatively deep pockets, did not prove convincing enough for Tokyo to get the coveted F-22. Congress repeatedly squashed the idea due to fears that the F-22 contained too much secret technology to share with even Washington's closest friends.

"Japan wanted the F-22, but Congress didn't agree to that," Yoshioka said. "We realized that it was important for us to develop our domestic capabilities."

China and Russia, meanwhile, have made great strides toward perfecting advanced stealth fighters that could rival the F-22, out-fly Japan's aircraft and — coupled with other rapid advances now under way, particularly by China's navy — tip the regional balance of power.

China surprised experts when it sent a stealth fighter, the Chengdu J-20, up for a test flight in January during a high-profile visit to Beijing by U.S. Defense Secretary Robert Gates.

The J-20 resembles the F-22 in many respects and has caused a great deal of consternation among U.S. and Japanese military planners because its development appears to be going faster than forecast. Its first flight came amid rising nervousness over Beijing's heavy defense spending, overall military modernization and increasingly assertive stance on territorial issues.

Though the J-20 is still years away from combat readiness, it could complicate efforts to control potential conflicts over Taiwan or North Korea and dramatically improve China's air defenses.

Russia's new fighter, the Sukhoi T-50, took to the air last year. It is being jointly developed with India's air force. The T-50 is seen not only as a boost to Russian air power — which is of concern to Japan because of a lingering dispute over islands both claim in the north Pacific — but also as a strong indication that it wants to sell more top-of-the-line fighters abroad.

Japan's own air force is rapidly aging.

Tokyo wants to replace its old F-4EJ and F-15 fighters with more current aircraft, most likely the U.S.-built F-35 Joint Strike Aircraft or F/A-18, or the Eurofighter "Typhoon." A much-delayed decision worth billions of dollars on which plane it will select is expected soon.

Japan's ATD-X program — the acronym stands for advanced technologies demonstrator — is not aimed at supplanting those acquisition plans. Instead, a domestically made stealth fighter would provide an alternative for a third fighter Japan uses — the domestically produced F-2.

Officials stress that it also is crucial for Japan to hone the ability of its engineers to build a state-of-the-art fighter if foreign sources refuse to sell — like Washington did with the F-22.

"It is extremely important to maintain and improve domestic fighter production and technology bases," the Defense Ministry said in an outline of the ATD-X program released in late 2009, when development began in earnest.

Another big consideration is money.

The Defense Ministry expects the economic impact of domestic research, development and production to reach 8.3 trillion yen ($101 billion) and create 240,000 jobs.