The Army's top political commissar declared today that China's defense capability lags 20 years behind more modern forces, and he called for a military shake-up to improve preparedness for war.

The call by Gen. Yu Qiuli contained the most cohesive outline for reforming the bloated and outdated armed forces since the national leadership of Deng Xiaoping began turning its attention to defense modernization last year.

Yu urged promotion of younger, educated officers, development of better weapons, regularization of procedures for demobilizing old officers, emphasis on scientific training, tighter political discipline and streamlining of communications between the services. However, Yu couched his proposals within the limitations of modernizing a huge bureaucracy--the Army's 4.2 million soldiers make it the world's largest military force.

"The People's Liberation Army would not be able to match a better equipped aggressor even if it modernized its weaponry over the next 10 to 20 years," Yu said in an article published in Liberation Army Daily. As a result, he said, the military should be streamlined and professionalized in line with the practical recommendations set forth by Deng in a book of speeches released earlier this month.

Deng, the nation's foremost political leader and head of the military's ruling commission, has set a major goal of reforming the largely peasant Army--whose aging officer corps was weaned on Mao Tse-tung's theories of guerrilla war.

In his book, Deng emphasizes that Mao's preparation for "a war of millet and rifles" is no longer relevant in today's world of missiles and rockets. Instead, Deng advocates reforms that would make for a better led, better coordinated and better equipped military: age limits for division-level and regimental-level officers, promotion on the basis of competence not seniority, modern weapons and beefing up of military academies.

With defense spending held down to allow for investment in other sectors, Deng has pushed for less costly improvements in organization, personnel and training.

Deng started the streamlining at the top last year, sacking the aged defense minister, Air Force and Navy commanders and three regional military commanders. The reforms have begun trickling down, with over 800 college-educated officers promoted to leading posts in the Air Force. But fundamental restructuring, according to diplomats in Peking, awaits the kind of organized shake-up urged by Yu, the director of the Army's political department.