Military officials say four U.S. soldiers were killed by a roadside bomb in eastern Afghanistan Monday, making July the deadliest month of the war for U.S. forces.

In southern Kandahar province, NATO said a British fighter jet crashed at the coalition's largest base.  The two pilots were injured while ejecting from the aircraft.

On Sunday, a British soldier was killed in an explosion in southern Helmand province.

In Washington Monday, U.S. Defense Secretary Robert Gates said he was "disgusted" at the Taliban's release of a video showing a captured U.S. soldier.  

Gates said the U.S. military is sparing no effort to find the missing man.  Private Bowe Bergdahl is the first U.S. soldier to be captured in Afghanistan.

The top U.S. military officer, Admiral Michael Mullen, said intelligence officers are studying the video.  He did not elaborate.

Taliban insurgents posted the 28-minute video on a Web site Saturday.  Bergdahl went missing from his base on June 30.

U.S. Secretary of State Hillary Clinton, who is on a trip to India, called the video "outrageous" and said it was a "real sign of desperation" on the part of the militants.

Meanwhile, outgoing NATO chief Jaap de Hoop Scheffer warned that terrorism would spread through the region and the world if NATO forces fail in Afghanistan.

Scheffer, who is London for talks with Prime Minister Gordon Brown, said al-Qaida would have a "free run again", adding their terrorist ambitions are global.

In recent weeks, 4,000 U.S. Marines, along with British and Afghan troops, have launched a major offensive in southern Helmand province, targeting Taliban insurgents in their traditional strongholds.

Some information for this report was provided by AFP, AP and Reuters.