WASHINGTON.-Pakistan is sending a senior economist here to persuade the Nixon Administration to resume economic aid suspended on March 26 when the civil conflict there erupted. United States economic aid to Pakistan has totaled more than $4.5-billion over the last 20 years and has been running at $200 million a year. A new loan of at least $70 million for commodity imports is still under Administration review.

The Pakistan government, moreover, is reported ready to carry out recommendations of the United States, the World Bank, the international Monetary Fund and other international donors for a 100 per cent devaluation of its currency, from 4.6 rupees to the dollar to more nearly 9, 10 or 11. While promising to devalue, it has avoided doing so three times in the last year, informants say.

M, M. Ahmed, top economic adviser to Gen. Agha Mohammad Yahya Khan, President of Pakistan, is expected to sound out American reaction to a fresh aid package when he confers at the White House tomorrow with Henry A. Kissinger, Presidential Assistant for National Security Affairs. Mr. Ahmed is also hoping to see Mr. Nixon.

WHITE HOUSE IS SILENT

The White House declined today to confirm or deny that Mr. Ahmed would arrive in the United States from Islamabad today and would confer with Mr. Kissinger tomorrow.

The exact package being sought by Pakistan was not known, but financial sources said that it would probably exceed the $450 million that an 11-nation consortium headed by the World Bank and including the United States provided annually to keep Pakistan solvent. A further $200-million to $400-million has been held up by the consortium for a year pending Pakistan's decision on devaluation, informants said.

The dispatch here of Mr. Ahmed is said to reflect the growing financial strains caused by the government's use of troops March 25 to crush a move for political autonomy in East Pakistan. Widespread loss of life, property damage and economic disruption have been reported.

The Pakistani Army, whose use of American supplied arms has been confirmed here by officials, has apparently arrested Sheikh Mujibur Rahman, head of the Awami League, which sparked the autonomy movement among 73 million East Pakistanis, predominantly of Bengali stock.

The rest of the Awami League leadership, however, is said to be intact, moving surreptitiously from town to town to avoid arrest by the Punjab-dominated army and seeking to organize resistance to the army's operations.

MUJIB ASSOCIATE HERE

Meanwhile, a leading East Pakistani economist and publicist, closely aligned with Sheikh Mujib, has arrived here to seek public support for an early end to hostilities and for Pakistani negotiations with the Awami League for East Pakistani independence.

His name is Rehman Sobhan and his efforts to see officials in the White House, State Department, aid agencies or other branches of the administration have been turned down.

Nonetheless he has been in contact with influential legislators including Senator Edward M. Kennedy, Democrat of Massachusetts, and he is scheduled to confer this week with Senator J. W. Fulbright, Democrat of Arkansas, chairman of the Foreign Relations Committee, as well as with staff aides.

"The Punjab seem to be going for the White House and the Bengalis for the Senate," one highly informed source observed.

Other informants disclosed that Mr. Ahmed is not the only top envoy that the Pakistani Government is now sending abroad in its search for emergency assistance, They noted that Arshad Hussein, former Foreign Minister, is touring Moscow, Paris and London conferring with financial officials.

However Mr. Ahmed, who has drafted previous five-year economic plans for Pakistan, is considered the key envoy in the current drive for foreign aid.

DEBTS TOTAL $4 BILLION

Mr. Ahmed is reported, for instance, planning to ask the World Bank, I.M.F., the United States and other foreign creditors for permission to pay $60-million due them May 1 in rupees, with payment in hard currency postponed for at least six months. Pakistan's total foreign indebtedness is said to exceed $4 billion.

Financial sources here point out that while Pakistan has repeatedly averted devaluation over the last year, the government has, during the same period, ordered $100 million in foreign arms, including 30 French Mirage jet fighters. The French suppliers are now being asked to postpone payment, sources add.