KARACHI, Pakistan, Aug. 23 —Pakistan's President, Gen. Agha Mohammad Yahya Khan, has asked his countrymen to donate blood for “all contingencies,” and political observers herb saw the appeal as veiled warning that war with India might be imminent.

Under banner headlines, Pakistani newspapers reported the President's appeal today and said that other signatories included East Pakistan's Governor, Lieut. Gen. Tikka Khan, and a number of right‐wing Moslem politicians.

During the last few days, the Government has announced series of blackout and air‐raid drills in principal Pakistani cities.

According to various unofficial sources, Sheik Mujibur Rahman, imprisoned leader of East Bengal's outlawed Awami League, is now on trial at military garrison near Lyallpur. An announcement of his conviction on charges of “waging was against Pakistan” is likely to create tension in East Pakistan and in the already hostile Pakistani‐Indian relations.

Border tensions have fol lowed the Pakistani Army's efforts to crush the East's secessionist movement, which began in March, and the flight of what is estimated to be more than seven million Pakistanis into India.