When a Japanese coast guard cutter spotted a small Chinese aircraft flying above disputed East China Sea islands in December, Japan's air force scrambled eight F-15 fighter jets, but they reached the scene only after the intruder had left. Japan's radar or surveillance planes had missed the low-flying aircraft entering what the nation considers its airspace, causing a delay in scrambling.

The embarrassing incident underscores the need for Japan to beef up the defense of air, sea and land in its southwest, said Gen. Shigeru Iwasaki, the top uniformed official of Japan's military, known as the Self-Defense Forces. He said China's navy and air force have been gradually shifting activities closer to the waters and skies near Japan's southwestern islands and "establishing a tenacious presence" in what's becoming an increasingly contentious part of Asia-Pacific.

"I believe we have an extremely good defense system but we still can't say it's perfect," Gen. Iwasaki, Chief of Staff of the SDF's Joint Staff said Thursday. "On Dec. 13, we allowed [China's] intrusion into our airspace. We need to strengthen our defense capability so there will be no such holes."

Gen. Iwasaki and the 250,000 troops of the SDF have gained a powerful ally. The conservative government of Prime Minister Shinzo Abe returned to power last month pledging an assertive foreign policy to counter the growing military threat of China and North Korea. Since then, the nationalist leader has unveiled a series of steps to strengthen Japan's military, long constrained by the country's pacifist constitution and fiscal austerity. In a move that would boost Japan's military spending for the first time in a decade, the defense ministry said Friday that it had requested a 2.2% increase in its budget to a minimum of ¥4.706 trillion ($52.9 billion) for the next fiscal year starting April.

According to the Stockholm International Peace Research Institute, Japan's military spending ranked sixth in the world in 2011, the most recent comparative data available, trailing the U.S., the top spender at more than $700 billion, and China, which ranked No. 2 at about $170 billion.

In addition to seeking more funds for defense next year, the new Japanese government is adding more for the current fiscal year by requesting ¥180.5 billion for weapons purchases and other defense purposes as part of an emergency economic stimulus package.

On the new shopping list: a new submarine, a destroyer and surveillance planes for the navy; more aerial radar capabilities for the air force by upgrading such equipment as airborne warning and control system (Awacs), and early waning aircraft known as E-2C. The army will conduct more drills for island defense and prepare new bases in places such as Yonaguni, an island less than 100 miles from the disputed islands, known as Senkaku in Japan and Diaoyu in China.

"Prime Minister Abe has instructed us to defend at any cost our people's lives, property, territorial land, waters and skies," Gen. Iwasaki said in the interview, his first with the foreign media since taking the top job a year ago. "Accordingly, we want to strengthen our posture in the southwest, particularly around the Senkakus."

That was the scene of the failed December scramble. Gen. Iwasaki, a compact-built air force commander who still sometimes pilots an aircraft when traveling for work, said the Chinese patrol plane had escaped the nearest land-based radar by flying at an extremely low altitude. This, he said, underscored the need for more aerial monitoring, both from aircraft and satellite.

China isn't the only nation worrying the 59-year-old four-star general. North Korea remains "unpredictable in its intent," even as the rogue nation increases the frequency of missile launches under the pretense of satellite testing.

Russia's air force and navy have been stepping up activities in the Far East , after remaining dormant for a decade and a half following the fall of the Soviet Union, Gen. Iwasaki said. "Russia sees itself as part of Asia," he said. "I think Russia has joined the race for various concessions in this region."

To its north, Japan has a separate territorial dispute with Russia, and Japan's air force conducted 247 scrambles against Russian planes in the year ended March, more than double the levels seen before 2007. That is higher than the scrambles prompted by Chinese aircraft. That tally hit 156 last year, compared with 96 and 38, respectively, in the previous two years, according to the defense ministry.

"After the Cold War, we optimistically assumed we'd be collecting a dividend of peace," Gen. Iwasaki said. "The reality has been a lot tougher."

Since the latest flare-up of the island dispute in September, Beijing has stepped up provocations by sending in maritime patrol ships with more frequency and boldness. After Tokyo protested a 13-hour stay of Chinese boats in territorial waters around the Senkakus on Jan. 7, Beijing responded with an announcement that its State Oceanic Administration would conduct "regular patrols" near the islands. On Thursday, Chinese fighter jets were spotted near Japan's airspace, according to the Japanese media, prompting scrambles by the Air SDF.

Asked to comment on a recent Japanese media report that air force jets might be allowed to fire warning shots at Chinese planes entering Japanese airspace, Gen. Iwasaki said Japan would follow procedures set by the International Civil Aviation Organization to respond to such cases. He didn't elaborate further.

Gen. Iwasaki stressed, however, that Japan intends to rely on its civilian Coast Guard ships to patrol the sensitive waters while keeping its military naval ships at distance to avoid escalation of the confrontation. "I think the hurdle is high for the deployment of the Maritime SDF." He added that in order to prevent unintended scuffles from escalating into full-scale crises, Japan and China should establish a maritime contact mechanism and agree on a procedure to contact each other in case of an emergency. Bilateral talks on such steps have been suspended since last fall.

"We have never closed our window for dialogue and defense exchanges," Gen. Iwasaki said. "We are ready for such steps whenever they are."