President Clinton has approved a substantial increase in the amount of money his administration will spend on security for American diplomatic missions overseas and will ask Congress to begin providing the additional funds much sooner than previously planned, senior officials said yesterday.

The administration's original plan to spend $3 billion over five years beginning in fiscal 2000 was denounced as inadequate by key members of Congress and by retired admiral William J. Crowe, who headed the State Department panels that investigated last year's lethal bombings of the U.S. embassies in Kenya and Tanzania.

The revised plan, which the president will send to Congress next week as an amendment to his proposed fiscal 2000 budget, calls for spending $11.4 billion over 10 years for design, site acquisition and construction of embassies and for hiring and training additional security personnel, administration officials said.

"This will be the most comprehensive and ambitious embassy construction program ever put in place," one senior official said.

He said the president's proposal will call for financing the embassy security program by cutting equal amounts of money from other programs, keeping the spending plan within budget limits set by the administration and Congress in their budget-balancing pact.

He declined to say what those cuts would be, but he said they would not come from the State Department or foreign aid budgets.

The truck bombs that devastated the embassies in East Africa, killing 224 people and injuring more than 5,000, exposed immense gaps in the security of U.S. diplomatic missions and embarrassed the State Department -- especially after it was revealed that the U.S. ambassador in Kenya, Prudence Bushnell, had pleaded for a new, more secure building but been turned down for lack of money.

Security standards recommended in a 1995 study, such as 100-foot setbacks from streets and a reduced ratio of glass to masonry on outside walls, had mostly not been implemented. The recent storming of the U.S. Embassy in Beijing after the mistaken NATO air attack on the Chinese Embassy in Yugoslavia spurred new concerns about the security of facilities flying the U.S. flag and their personnel.

Crowe's report on the East African bombings recommended outlays of $1.4 billion a year over 10 years to build some embassies and reinforce others.

Congress appropriated $2.1 billion in emergency security and counterterrorism funds last year, but Clinton's proposed 2000 budget allocated only $37 million specifically to construction and security upgrades. State Department officials argued that no additional construction money is needed in the first year because sites have not been acquired or designs approved. But House appropriators virtually demanded that the administration come back and seek more money, which it is now about to do.

The new plan calls for spending $300 million in 2000, and for raising the amounts to be sought in each subsequent year by $150 million. The $11.4 billion total over 10 years would be exactly equal to the amount recommended by Crowe.

"We're very pleased that the president is submitting this," Secretary of State Madeleine K. Albright said last night. "Everyone in the administration and on Capitol Hill understands the need for this."