By Phil Stewart ROME, July 4 (Reuters) - The United States sees suicide bombers in Afghanistan as a greater threat than any organised summer offensive by the Taliban, which has been weakened by the loss of key commanders, a U.S. official said on Wednesday. U.S. Assistant Secretary of State Richard Boucher said the Taliban's threatened spring offensive had failed to materialise partly thanks to military action and reconstruction efforts. It was also because the Taliban "gave their fighters a couple of weeks to a month off to go harvest (opium) poppy". "Then they came back in June and started talking about a summer offensive," Boucher said during a trip to Rome. "We will see attempts by them to organise ... But I think the greater fear has to be the suicide bombs. We have had some success in stopping that, but you can't stop the suicide bombers until you have real control over all the territory. "And we don't have that yet," he told reporters. Taking a lead from the Iraq insurgency, the Taliban have increasingly resorted to suicide and roadside bombings. They took heavy losses in conventional battles with U.S. and NATO forces last year. Suicide bomb attacks rose from 21 in 2005 to 139 last year and are expected to soar this year. A single Taliban bomber killed 24 people last month. Boucher praised greater efforts by Pakistan over the past six to nine months to secure its border area with Afghanistan, where Taliban and al Qaeda fighters have taken refuge. Afghanistan was also making a more concerted effort near the border, putting fresh pressure on the Taliban there, he said. "The fundamental story this year is that the government in Afghanistan has extended itself, the Pakistani government on its side of the government has extended itself, and the Taliban are under pressure on both sides," he said. Boucher was in Rome for a conference earlier this week meant to shore up Afghanistan's justice system, which was partly overshadowed by talk about civilian casualties. In the latest major incident this weekend, Afghan officials said 45 civilians were killed by a U.S.-led air strike, though the NATO-led International Security Assistance Force (ISAF) set the toll from the pre-dawn raid lower. "It entered into discussion from various quarters ... The NATO secretary-general was there, we were talking to him about it," Boucher said. "We certainly regret every incident and try to avoid them whenever possible. And we're working now with the Afghan government and the different forces in Afghanistan to try to do better."
