President Nixon met yesterday with a special emissary from Pakistani President Yahya Khan who is here to convince U.S. and international monetary officials to bail out the nearly bankrupt country that has been wrecked by civil war.

The emissary, M. M. Ahmad, is Yahya's top economic adviser. He is understood to have been carrying a letter from Yahya to Mr. Nixon, but the White House declined to give any details of the 30-minute meeting.

The White House only disclosed, in response to reporters inquiries, that the meeting was to take place.

Diplomatic sources said the message to Mr. Nixon contended that stories of large-scale massacres in East Pakistan have been grossly exaggerated, although Yahya reportedly conceded that his army's initial action was tough.

SANCTIONS SOUGHT

Yahya reportedly wrote that this was made necessary because East Pakistan's dominant Awami League party had been taken over by extremists. But, according to this account, of the message, he is ready to implement the party's six-point program for the province's autonomy once moderates are restored to control of the Awami League.

Ahmad's visit comes as congressional pressure is building against any U.S. aid to the Pakistan government that could contribute to repression of the secessionist movement in East Pakistan. The House Foreign Affairs Committee has scheduled hearings on Pakistani for today, with Sen. Edward M. Kennedy (D- Mass.) scheduled to testify Supporters of the breakaway Bangla Desh government, the East Pakistani exile government operating in India, advocate international economic sanctions against the Pakistani central government.

ARMS PURCHASES

These pro-Bengalis say they have found resistance to the idea in Washington because recent attempts at sanctions against such other governments as Rhodesia and South Africa have been ineffective. The pro- Bengalis reply that the comparison is faulty because those countries have viable economies.

The last official report on Pakistan's reserve position shows that it was down to $182 million in foreign currencies and $54 million in gold about two months ago.

It is widely assumed that the reserves have since been drawn by two thirds or more.

The central government has been using much of its precious currency to buy arms abroad. Informed sources say they have heard of at least one major purchase on the international arms black market-100,000 reconditioned rifles to arm the two million West Pakistani civilians living in East Pakistan.

Another Pakistani emissary, who was here a month ago, received a cool reception from the U.S. government, the World Bank and the International Monetary Fund.

The latest envoy is said to be proposing a number of measures, including devaluation of the Pakistani rupee by half or more; temporary payment to the International consortium Of Pakistan's creditors in rupees instead of in hard currency, and "association" of civilians, including "rational" elements from East Pakistan, with Yahya's military government.

In addition to Mr. Nixon, Ahmad has asked to see World Bank President Robert S. McNamara, Pierre Schweitzer of the International Monetary Fund, AID director John Hannah, Agriculture Secretary Clifford Hardin and Joseph J. Sisco, Assistant Secretary of State for Near East and South Asia.

The World Bank has been privately advocating the rupee devaluation for some months, according to monetary sources here. But some sources say this would probably be considered insufficient now and that more baste economic reforms would have to accompany the devaluation before the international monetary community would consider increasing its credits to Pakistan beyond the present level of more than $4 billion.

Ahmad is said to be proposing that the $60 million Pakistan is scheduled to pay the consortium over the next few weeks be paid in rupees, which would only become convertible into dollars in six months. But Pakistan is said to be indicating willingness to pay in dollars the 820 million it is scheduled to pay the World Bank.