ROME/SOFIA, March 7 (Xinhuanet) -- The United States faced new strains with allies on Monday when Bulgarian media said an investigation into the fatal shooting of a Bulgarian soldier in Iraq last week had showed that US troops were probably responsible.

    Washington has already been under fire from Rome after its troops shot dead Friday in Iraq an Italian intelligence agent who was accompanying a freed Italian hostage on the way to Baghdad airport.

    The Bulgarian solider was killed in southern Iraq on Friday, around the same time that US forces in Baghdad opened fire on a vehicle taking Italian female journalist Giuliana Sgrena to the airport shortly after her kidnappers freed her.

    Bulgarian Defense Minister Nikolai Svinarov said an investigation showed Bulgarian soldier Gurdi Gurdev had probably been killed by "friendly fire" from American troops.

    "Someone started shooting at our patrol from the west, and in the same direction, 150 meters away, there was a unit from the US army," he told a news conference.

    "The result gives us enough grounds to believe the death of rifleman Gurdi Gurdev was caused by friendly fire."

    Svinarov said the Bulgarian army's chief of staff had written to General Richard Myers, chairman of the US joint chiefs of staff,asking for an investigation.

    Bulgarian President Georgi Parvanov on Monday summoned US ambassador to Sofia, James Pardew, demanding a "serious" investigation to determine the responsibility for the incident.

    Parvanov said Bulgaria "will demand that those to blame assume their responsibility," Bulgarian Telegraph Agency quoted he as saying.

    The president pointed out that this incident revealed the existence of serious problems in coordination and collaborated actions of the coalition forces in Iraq.

    Pardew expressed his deepest regret over the shooting while promising to convey the position of Parvanov to Washington and theUS military in Iraq. He also expressed his hope that the incident would not affect the friendly ties between the two nations.

    Meanwhile, Rome renewed its demand for a full inquiry into the shooting by US troops that killed Italian agent Nicola Calipari and wounded journalist Sgrena and two Italian officials.

    Italian Prime Minister Silvio Berlusconi on Monday summoned once again the US ambassador to Italy to renew his demand for a full investigation, as the nation held a state funeral in Rome forCalipari.

    At the end of their 45-minute meeting, US ambassador Mel Sembler submitted a written report to Berlusconi, which may cover the results of initial investigation by the United States of the shooting, Italian press said.

    Shortly after the shooting, Berlusconi summoned Sembler on Friday and demanded an explanation. Sembler told Berlusconi he hadasked Washington for an immediate clarification and promised a thorough investigation.

    US President George W. Bush expressed his regret as he called Berlusconi, and promised that the shooting would be fully investigated, White House spokesman Scott McClellan told reporterson Friday night.

    Sgrena, who suffered shrapnel wounds in the shoulder, said it was possible that they were targeted deliberately because the US opposes Italy's policy of negotiating with kidnappers.

    But the White House rejected Sgrena's suggestion that the US troops might have shot them on purpose.

    "I think it's absurd to make any such suggestion that our men and women in uniform deliberately targeted innocent civilians," said spokesman Scott McClellan. "That's just absurd,"

    He said the road to the airport "is one of the most dangerous roads in Iraq" plagued by suicide bombings and other attacks, and that forces often had to make "split-second decisions to protect their own security."

    The US military said earlier the Italian vehicle was traveling at high speed and ignored instructions to stop. Sgrena disputed that account, saying there was no warning and that they were traveling at a moderate speed.

    US media quoted military sources as saying on Monday that the shooting was due to a "lack of communication" between intelligenceorganizations of the two countries. But Italian intelligence authorities said Washington should have had related information.

    The shootings triggered strong condemnation both in Italy and Bulgaria, where a large proportion of people opposed the US-led war in Iraq, despite their governments' support to it.

    Angry Bulgarians called on Washington to explain the circumstances of Gardev's death and some parties even demanded the parliament and government reconsider the Balkan country's militarypresence in Iraq.

    Protesters in Rome demanded a complete withdrawal of Italian troops from Iraq, and a thorough investigation into the shooting incident. The Italian press is crying over the "bitter price" the country paid for maintaining forces in Iraq.

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