A roadblock set up by Sens. Thomas F. Eagleton (D-Mo.) and Rudy Boschwitz (R-Minn.) yesterday prevented southern senators from rushing a new tobacco price-support bill through the Senate in near-record time.

Their objections to the speedy procedures forced Sen. Jesse Helms (R-N.C.), chairman of the Agriculture Committee, to agree to permit full debate on the measure after the July 4 recess--a pause that could give critics time to marshal their forces.

The bill, introduced and passed in less than a week in the House, would revamp the tobacco allotment and price-support program in an effort to make it self-supporting at no cost to taxpayers.

Tobacco legislators justified the haste by saying the markets for flue-cured tobacco open July 15. They want the new program enacted before then, due in part to concern that uncertainty may upset markets and force the government to buy costly new stocks of unsold leaf.

But Eagleton, a fierce critic of the tobacco program, complained that Helms and other tobacco-state legislators were rushing the bill at "an almost record pace...a pell-mell rush" without adequate opportunity for Senate discussion.

He said that while the bill proposed important changes, it didn't go far enough to correct potential abuses and distortions of last year's congressional directive that the program be operated without tax subsidy.

Eagleton threatened to keep the Senate in session indefinitely to prevent the tobacco bill from being called to a vote before the holiday recess. He milled around on the floor for almost two hours with Helms and other tobacco-state senators before getting his way.

Boschwitz made similar complaints about procedures earlier in the day, before walking out of an Agriculture Committee meeting that Helms called without public notice to rush the bill to quick approval. No Washington hearings have been held on the legislation.

Boschwitz traded testy barbs with Helms over the committee's procedures before departing and leaving the panel without the necessary quorum to approve the bill. Helms suggested that Boschwitz, by tangling with tobacco, would have trouble winning votes on dairy legislation he is backing.

A later arrival, Mark Andrews (R-N.D.), restored the committee's quorum and the measure was adopted with minor amendments in less than half an hour.

After Eagleton and Boschwitz got their way on the floor, Senate leaders had to make another deal--this one on sugar--to free tobacco from further threat. Sen. Dan Quayle (R-Ind.), a potential tobacco objector, was promised that his now-stalled bill to eliminate the sugar support program would get full Senate consideration.