SHANNON, Ireland, Nov 2 (Reuters) - U.S. Secretary of State Condoleezza Rice on Friday defended her decision to force U.S. diplomats to serve in Iraq and said they had an obligation to take on such difficult assignments.

Many diplomats are incensed following a U.S. State Department decision last week to identify "prime candidates" who may have to accept compulsory one-year tours in Iraq or risk losing their jobs.

In her first public comments on the staffing directive, Rice conceded it was a "sensitive issue" but said people must serve where they were needed and Iraq was a priority.

"In a sense, the fact that so many people have volunteered and have served, I would hope others would think about their obligation not only to the country but to those who have already served to make sure that these difficult assignments are shared across the service," Rice told reporters traveling with her to Turkey where she will attend a conference on Iraq.

More than 200 diplomats have been told they are in a pool of people who may be forced to go to Iraq to fill 48 positions for which no qualified candidates have volunteered.

At an emotional meeting at the State Department on Wednesday, diplomats complained about the enforced assignments and questioned why they read about the move via news reports rather than heard from Rice herself.

One diplomat said it was a "potential death sentence" to serve in Baghdad. Mortar rounds frequently land in the heavily fortified "Green Zone" where the U.S. embassy is located.

"I am very sorry that the recounting of the comments of a few people left the impression that somehow the Foreign Service doesn't want to serve in Iraq," said Rice before a refuelling stop in Ireland.

"It couldn't be further from the truth and on behalf of those who are serving, I want to say how much their service is appreciated," she added.

More than 1,500 U.S. diplomats -- out of a total of about 11,500 -- have served in Iraq, some of them doing several tours since the U.S. invasion in March 2003.

"People are serving and they are serving very, very well and they are serving with great bravery," said Rice.

Rice sent a cable herself late on Thursday urging staff to go to Iraq and she said there had been several volunteers since the staffing decision was made last week.

"I don't know if we will have to direct assignments or not. We are one Foreign Service and people need to serve where they are needed."

Many U.S. diplomats are reluctant to accept postings in Iraq because of the dangers of working in a war zone and the fact that they are separated for lengthy periods from their families who are not allowed on such hardship missions.

The top U.S. diplomat said everything possible was being done to protect diplomats, including providing fortified facilities and air cover where needed.

"We are doing everything that we can to try and protect our diplomats but this is the one of the highest priority tasks for the United States and we are going to meet our obligations," she said.