The effort to win over Afghans on former Taliban turf in Marja has put American and NATO commanders in the unusual position of arguing against opium eradication. From Gen. Stanley A. McChrystal on down, the military's position is clear: U.S. forces no longer eradicate," as one NATO official put it. Opium is the main livelihood of 60 to 70 percent of the farmers in Marja. American Marines occupying the area are under orders to leave the farmers' fields alone. United Nations drug officials agree with the Americans. Pictures of NATO and other allied soldiers "walking next to the opium fields won't go well with domestic audiences, but the approach of postponing eradicating in this particular case is a sensible one," said Jean-Luc Lemahieu, who is in charge of the United Nations Office on Drugs and Crime here. Though the United States government's official position is still to support opium crop eradication in general, some American civilian officials say that the internal debate over Marja is far from over within parts of the State Department and the Drug Enforcement Administration. A spokesman for the United States Embassy in Kabul, Brendan J. O'Brien, said officials would decline to comment while the matter was under review.