Four Americans and a Briton were killed in southern Afghanistan on Wednesday, military officials said.
The four U.S. service members were killed when their helicopter was downed by hostile fire in Helmand province, said International Security Assistance Force spokesman Lt. Col. Joseph T. Breasseale.
The British soldier was killed in an explosion, also in Helmand province, the British Ministry of Defence said.
June is turning into a deadly month for international forces in Afghanistan - 29 service members, including 19 Americans, have been killed, bringing the American death toll in Afghanistan to more than 1,000, according to CNN's calculations.
"It's been a tough week," said Pentagon spokesman Bryan Whitman. "Our operational tempo is at an all-time high. We try to do everything to prevent casualties, but we have active operations and more forces there than ever in the past."
The U.S. and coalition countries will have to show signs of progress in Afghanistan by this winter or risk losing the support of the public, said U.S. Defense Secretary Robert Gates on Wednesday.
"I think that it is probably a reality that in virtually all of the coalition countries the publics are going to expect to see some progress this winter, some sign that we are moving in the right direction. I think that the voters are sophisticated enough to know that we’re not going to be done, they’re won’t be victory and that we still have a long road to hoe," he said in London ahead of meetings with NATO allies. "The one thing that I think none of the publics, and I would say including the American public, will tolerate is the perception of a stalemate in which we’re losing young men."
Last December, President Obama outlined a strategy for Afghanistan that would begin to bring U.S. forces home in July 2011, but with no definite date on when the last troops would leave.
He also addressed the Taliban: "At this point the Taliban are part of the political fabric of Afghanistan and to adopt a strategy that basically says we're going to eliminate the Taliban I think is unrealistic."
Listen to more from Gates as he discusses the tough summer ahead in Kandahar, the Taliban and the recent attack on a NATO convoy in Pakistan.