WASHINGTON, April 8 (Xinhuanet) -- As fighting between the US-led coalition forces and Shiite Muslim militiamen south of Baghdad leads to rising causalities in the field and a fall in President George W. Bush's poll numbers at home, the Bush Administration is facing a major test in Iraq, observers say.

    March was the second deadliest month for US forces in Iraq since Bush declared an end to major combat last May, and April started off with the heaviest fighting since the Iraq war that ousted Saddam Hussein a year ago and with heavy casualties on bothsides.

    The surge of violence since April 4 has led to the death of more than 30 coalition soldiers, including more than 20 US soldiers, and over 170 on the Iraqi side. Over 600 US troops have so far been killed in Iraq since the war began on March 20, 2003.

    The rising casualties of US troops have taken a toll on Bush. Apoll released Monday by the Pew Research Center for the People & Press showed Bush's overall job approval has dropped to 43 percent,a low point for his presidency, and more than half of Americans disapprove of the way he is handling Iraq.

    The rising causalities among the coalition troops show that theforces of the anti-coalition insurgents have been growing, observers say.

    "We face a very well-organized network which has the knowledge,materials and logistics to organize terrorist attacks," Polish President Aleksander Kwasniewski said of Iraq's insurgents on April 2. "The threat is realistic," Kwasniewski told Poland's Radio One.

    Poland sent combat troops for the US-led Iraq war and now leads a 9,500-strong multinational force in Iraq.

    What is more ominous for the US-led coalition troops is that they are now confronting the Shiite Muslims who initially welcomed them after decades of ruling by Saddam's Sunni-dominated regime.

    The spread of violence has sounded alarm for coalition forces, already burdened by a Sunni insurgency of Saddam Hussein's remnants. A full revolt among Iraq's 15 million-plus Shiite Muslim would spell disaster for the US-led coalition.

    As a result of the causalities of US allies in Iraq, diplomatic strains have emerged as many countries that dispatched smaller forces to Iraq began to question their roles in Iraq.

    South Korea has ordered its personnel to suspend activities outside military camps. The Ukrainian government said its troops were evacuating Kut. Bulgarian President Georgi Parvanov called anemergency meeting of top military officials Wednesday to review the security of Bulgarian troops in Iraq. The government of Kazakhstan has announced it would not extend its presence beyond May.

    All these developments amount to a severe challenge for Bush, who have vowed to stay course in Iraq and hand over sovereignty toan interim government on June 30.

    If the security situation in Iraq fails to improve markedly by November, Bush's chance of winning re-election will be surely undermined, observers say. Enditem