A split among Senate conservatives torpedoed a deal with the White House on Foreign Service nominations yesterday, forcing the Senate to postpone action on 29 ambassadorial and policy appointments until after the Fourth of July recess.

Several key nominations have been held up by the impasse, including those of John C. Whitehead to be deputy secretary of state, Thomas R. Pickering to be ambassador to Israel, Richard R. Burt to be ambassador to West Germany, Rozanne L. Ridgway to replace Burt as assistant secretary for European affairs, and Elliott Abrams to be assistant secretary for inter-American affairs.

"It's just a struggle between these Republican senators and the secretary of state," said Majority Leader Robert J. Dole (R-Kan.) after the Senate adjourned. "There's no winners or losers except those poor guys stuck on the Senate calendar."

Sen. Jesse Helms (R-N.C.) led a group of nine conservative senators in objecting this month to what they called an "ideological purge" of conservatives in recent State Department job shifts. They insisted that six conservative diplomats be "taken care of" with new or continuing jobs, and they put a "hold" on all 29 Senate floor confirmation votes until the jobs are secured.

After a series of meetings this week -- among the senators, Senate leaders, Secretary of State George P. Shultz and President Reagan -- White House chief of staff Donald T. Regan began working to find the jobs. All sides expected to be able to hold confirmation votes yesterday.

But by early afternoon, according to Senate aides close to the fracas, Regan had nailed down only three jobs among the six people: refugee coordinator Eugene Douglas and Ambassador to Mexico John A. Gavin would remain in their current posts, and former UNESCO ambassador Jean Gerard would be nominated ambassador to Luxembourg.

Left "unprotected," the aides said, were Ambassador to Paraguay Arthur H. Davis, Ambassador to Uruguay Thomas Aranda Jr. and James L. Malone, assistant secretary for oceans and international environmental and scientific affairs.

Helms then wrote to Dole, offering to lift the hold on 14 of the pending nominations, including Pickering, Whitehead and Abrams. "John D. Negroponte nominated to succeed Malone can be added to the above list provided I receive assurance from Don Regan and Secretary Shultz that Jim Malone will be nominated for ambasssador to either Panama or Belize," Helms' letter said.

This led one tired Senate staff aide to quip, "We'll release half of our hostages and they'll release half of theirs."

However, Dole said other senators in the conservative group, including Sens. James A. McClure and Stephen D. Symms, both of Idaho, objected to some names on Helms' list.

The State Department also objected to clearing only a partial list, according to Dole. "Shultz said all or none," he said. Consideration will now occur no earlier than July 10, Dole added.

Sen. Christopher J. Dodd (D-Conn.) said the Senate's inaction would be remembered as "a day of disgrace" if there should be any harm to the 39 U.S. hostages in Beirut that might have been prevented by having Pickering on the job in Israel.

"It is a mistake of significant proportions" to hold up the nominations "for very petty reasons," he said.