The United States and China remain close to an agreement on a major purchase of American grain despite Chinese irritation over news leaks about the negotiations, Agriculture Department officials said yesterday.

The department recently stepped up its efforts to conclude the agreement, sending two top officials, Thomas Saylor and Donald Novotny, to Peking.

This fed assumptions that the Carter administration hoped to conclude the talks before Election Day. A commitment by China to purchase 6 million to 9 million metric tons of grain annually over the next three years presumably would improve President Carter's standing in the farm states.

Saylor, however, is headed home; with the agreement as yet unsigned, Agriculture Department officials said.

Government officials, asking not to be identified, say the Chinese delayed the signing because they were irritated over news leaks last Friday. about the negotiations and saw this as an attempt to pressure them into an early agreement.

An additional source of friction is a new State Department agreement granting special diplomatic privileges to representatives of the private organizations that handle trade and cultural relations between the United States and Taiwan. China officially protested that action Wednesday.

Several Agriculture Department officials insisted that the grain agreement is not in jeopardy, however.

"The talks are continuing, but nobody expected the agreement to be concluded overnight," said Tom Sand, special assistant to Agriculture Secretary Bob Berland.

Sand said a short delay had occured because of translation problems, but the administration still expects the agreement to be concluded soon, possibly by next week. "We see no snags," said another official.

The immediate impact of the agreement would be more symbolic than real. The Chinese already have purchased about 6 million metric tons of grain from the current U.S. crop since June 1, said Martin Abel, vice president of Schnittker Associates, a Washington-based agricultural consulting firm. The agreement merely would confirm exports at this level initially.

However, it does lock in Chinese purchases of U.S. grain at fixed levels during the next two years, and that will be regarded as a plus by grain farmers, Abel said. It also helps stabilize future grain exports, providing further protection against sharp swings in demand and prices, he added.

The political impact of a pre-election agreement is hard to assess, said Margie Williams, governmental affairs director of the National Association of Wheat Growers.

A new grain deal with China gives Carter a way of meeting the lingering resentment among farmers over the Soviet embargo, Williams agreed.