The blockade by conservative senators of some of President Reagan's foreign service nominations collapsed yesterday after Reagan met with the Senate leadership and several committee chairmen to urge speedy confirmation.

White House chief of staff Donald T. Regan was reported to be working on obtaining or preserving jobs for conservative diplomats whom the senators had sought to protect.

Majority Leader Robert J. Dole (R-Kan.) said the White House session produced "a lot of progress." He said he hoped that several nominees would receive final Senate approval today, and Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.) said his committee would probably approve several other nominees.

Key nominations delayed in the month-long wrangle and likely to receive final approval today include those of Thomas R. Pickering as ambassador to Israel, Richard R. Burt as ambassador to West Ger-many, Rozanne L. Ridgway to succeed Burt as assistant secretary of state for European affairs and Richard T. McCormack to be ambassador to the Organization of American States.

Nine conservative Republicans led by Sen. Jesse Helms (R-N.C.) objected earlier this month to what they called an "ideological purge" of conservatives from ambassadorships and other diplomatic posts in recent reshufflings.

The senators placed a "hold" on all confirmations, invoking a senatorial courtesy that allows any member to delay consideration of a nomination. They let it be known that their price for lifting the hold was assurance that endangered conservatives would be "taken care of," either in their current jobs or elsewhere.

According to sources close to the debate, some of those include Arthur H. Davis Jr., ambassador to Paraguay; Thomas Aranda Jr., ambassador to Uruguay; former UNESCO ambassador Jean Gerard; James L. Malone, assistant secretary of oceans and international environmental and scientific affairs, and John A. Gavin, ambassador to Mexico.