A team of U.S. experts will travel to Cambodia July 24 to examine the remains of what may be U.S. servicemen unaccounted for from the Vietnam War, says Sen. Charles Robb, D-Va. Robb, a Vietnam veteran, visited Cambodia earlier this year to appeal for cooperation in obtaining an accounting of the 83 Americans missing and believed dead in that country. The visit is the first of its kind since the communist triumph in Cambodia in 1975. Meanwhile, a bipartisan group of leading senators, fearing a return of the Khmer Rouge to power, has drafted a letter urging President Bush to change the administration's policy toward Cambodia. ``The president's policy in Cambodia is indefensible,'' Senate Majority Leader George Mitchell, D-Maine, a leader of the petitioners, told reporters this week. ``How can we, the United States, which has already enacted into law a prohibition on aiding the Khmer Rouge, engage in a policy which does precisely that?'' said Mitchell. A draft of the letter urges Bush to open the door to some contacts between the United States and the government of Hun Sen in Phnom Penh. The United States supports a coalition of groups that are fighting the Cambodian government and the Khmer Rouge, who slaughtered more than a million Cambodians when they ruled the country in the 1970s. The United States has received cooperation from Vietnam and Laos on the MIA issue. All told, the 2,302 missing Americans are believed to be in those two countries and Cambodia. State Department spokesman Richard Boucher said he did not know how many sets of remains the American experts will be invited to examine in Cambodia. He said the mission was strictly humanitarian in nature. But a senior State Department official, asking not to be identified, said the gesture by the Cambodian government apparently was aimed at achieving increased international recognition. There has been no American presence in Cambodia since the U.S.-backed government was ousted by the Khmer Rouge rebels in April 1975. The Khmer Rouge was ousted by Vietnamese forces in 1978 after 3{ bloody years in power. Boucher said that if any of the remains appear likely to be those of Americans, a U.S. Air Force plane will repatriate them to Hawaii for further analysis. ``We appreciate the support of the Phnom Penh authorities for this undertaking, which we consider an important humanitarian endeavor, and, if successful, will help alleviate the continued uncertainty of the families of the missing Americans,'' Boucher said. Robb, who had met with Hun Sen and other officials in Phnom Penh, made the announcement in a speech Friday to the National League of American Prisoners and Missing in Southeast Asia, which is holding its 21st annual meeting in Washington. ``This is obviously only the beginning of a process which we hope will allow for the accounting of every missing American,'' Robb said.