BOSTON – Gov. Mitt Romney is pulling back on threats to lay off 100 workers at the Department of Social Services and slash spending for homeless shelters and youth services.

In a letter to Senate Majority Leader Frederick E. Berry, Romney said he would not cut the programs because Senate leaders had assured him they would approve an emergency spending plan within the next 10 days.

“Based upon these assurances, I will operate these programs under the assumption that they will be fully funded, recognizing that we are spending above your appropriation,” Romney wrote. “The programs will run out of money entirely in March if funding is not restored by the Legislature by that time.”

Romney’s cuts would have left adults with serious mental illnesses without housing and would have forced the Department of Youth Services to eliminate 85 beds for juvenile offenders.

Earlier this month, Berry sent Romney a letter urging him not to make the cuts. Yesterday, Berry said the governor had stopped “playing politics.”

“He rethought the situation and saw it would start a crisis,” said Berry, D-Peabody.

State Health and Human Services spokesman Dick Powers said the agency has already starting carrying out Romney’s orders to cut back. The effort ended immediately yesterday.

Beds for juvenile offenders that had not been filled per Romney’s request were to be filled last night, Powers said. Letters that the Department of Mental Health had sent to private, state contracted mental health homes to reduce their contracts were being rescinded, and layoff letters meant for Department of Social Services workers would not be sent.

Senate President Robert Travaglini has said he hopes to get the supplemental spending plan to Romney by the end of the month, including money for rape crisis centers.

The administration has initially given the Legislature a Sept. 15 deadline to approve the extra money, warning that it would be forced to lay off 41 attorneys, 50 social workers and 11 central office employees at the Department of Social Services to save $6.4 million.

The administration also threatened to phase out programs at the Department of Youth Services, for a savings of $3.1 million, and reduce payments to six homeless providers in Greater Boston and western Massachusetts for a savings of $1.5 million.

Material from the Associated Press was used in this report.