Congressional conferees wrapped up work yesterday on a new four-year farm bill, then ran into fresh budget warnings from the administration that could scuttle the measure.

The bill, covering commodity programs and rural credit and development activities, is about $681 million above the $10.6 billion Senate version that the White House had demanded the conferees adopt.

Even with that, and the estimated $6 billion in reductions that House conferees accepted, the administration continued its effort to force more cuts.

Department of Agriculture economist William Lesher told the conference, "We still have problems with your agreement . . . . I'm not here to say the secretary of agriculture will recommend a veto. All I'll say is things look grim."

The conferees are scheduled to meet again today to discuss possible further changes, but at least among House delegates there seemed to be bipartisan feeling that they had yielded as much as they could.

Said Rep. E. Thomas Coleman (R-Mo.): "The administration ought to declare a victory and get out. They've held our feet on the fire, and we've come down $6 billion. The department ought to be happy with what we've done."

Added Rep. Thomas S. Foley (D-Wash.) as the conferees adjourned last night: "The essential messsage is that the administration can't support anything but the Senate bill . . . . I cannot sign a conference report that is the Senate bill. It is time to decide if we are going to get a report."

The administration's principal objections to the bill are related to dairy price supports and grain target prices, the direct subsidy payments that farmers might be entitled to after fiscal 1982.

By administration estimates, the conferees went beyond the acceptable on wheat- and feed-grain support loan increases ($467 million above the Senate bill), dairy ($151 million higher), wool ($55 million higher) and peanuts ($9 million higher).

Still to be dealt with is a last-minute proposal by Sen. Jesse Helms (R-N.C.), the conference chairman, that would limit dairy supports for any year in the bill to $1 billion. USDA estimates that fiscal 1982 dairy supports will cost almost $2 billion.

Before the conference report reaches the White House, it faces more tough sledding in the House and Senate, where critics of various commodity sections--chiefly dairy, peanuts and sugar--are plotting to overturn the measure.

The last roadblocks, food-stamp spending levels and language covering meat import standards, were cleared aside yesterday after days of deadlock and fruitless debate.

The conferees took the easy way out on food stamps by authorizing the program for one additional year (fiscal 1982) instead of extending it through 1985. That was done when they could not agree on cost-of-living adjustments for 1983 and beyond. Helms had insisted on further cuts, but the House refused to heed him.

Before they dodged that issue, the conferees agreed to cancel a benefits increase that about 3 million food stamp beneficiaries would have received next July.

Administration officials said the delay until Oct. 1, affecting Social Security, Supplemental Security Income and veterans' benefits recipients, would save between $25 million and $40 million. House conferees argued in vain against the reduction.

The meat import issue was thornier, with the panel finally agreeing to language offered by Sen. John Melcher (D-Mont.) and strongly supported by the administration.

The Melcher approach requires that imported meat be subject to the same public health standards for chemical and drug residue as domestically-produced meat, with random inspections abroad and at U.S. ports.

Melcher conceded that the USDA is following his approach as a matter of policy but said his codification of the requirement assures more consumer protection.

He and USDA argued that stricter language proposed by Reps. Tom Harkin (D-Iowa) and Glenn English (D-Okla.) to ban import of meats produced with chemicals prohibited here, would invite retaliation by foreign buyers of U.S. agricultural products. "The real problem," said Harkin, whose position was supported by U.S. cattlemen and consumer groups, "is a lack of adequate inspections of imported meat. The sampling of imported meat is very much a random thing."