A critical shortage of diplomats will force the State Department to leave open 10 percent of its vacant positions around the world, with the exception of key posts such as in Iraq and Afghanistan.

At least 150 jobs in Washington and overseas missions scheduled to be filled next year will have to be deferred as the department struggles with "severe staffing shortfalls" due to a lack of resources, Foreign Service Director General Harry Thomas sent in a worldwide cable early Wednesday. The move comes even as the Bush administration is seeking to ramp up its international outreach.

"The department's staffing has not kept pace with current needs," he said in the unclassified cable entitled "2008 Foreign Service Assignments, Deficits and Tough Choices Ahead."

"Bureaus have been tasked with restrictions on 10 percent of midlevel generalist jobs in the current assignments cycle," Thomas said.

A copy of the cable was obtained by AP shortly after it was distributed through the State Department's internal messaging system.

Although keeping vacant positions open is not unprecedented — some embassies operate at only 70 percent of their full-strength staffing levels — the move follows a highly publicized dispute over the possibility of forced service in Iraq and comes as the department considers so-called "directed assignments" to other hardship posts.

"Critical new requirements (e.g. Iraq, Afghanistan, Libya) and a growing number of one-year jobs have translated into serious deficits" in qualified personnel at various seniority levels and specialties, Thomas wrote, noting that training requirements for numerous posts often cause delays in assignments.

Much of the problem, he said, lies with Congress, which has not authorized any significant increase in the size of the foreign service since 2004.

"At the same time, our requirements and training needs, particularly in hard and superhard languages, have proliferated," Thomas said. "We are, therefore, operating with significantly fewer people than positions."

"If we cannot fill every position around the world, we must fill those that are our highest priorities," he said, adding that he had ordered each bureau to determine by Monday which 10 percent of their positions to leave vacant.

Thomas asked that bureaus focus on domestic jobs, but conceded that overseas assignments may also have to go unfilled.