The number of U.S. and allied troops killed in Afghanistan in June has reached 40 -- the highest monthly toll of the seven-year-old war.

Defense Secretary Robert Gates says Pakistan recognizes the attackers are a problem.

The latest casualty came when a coalition service member on a reconnaissance patrol in western Afghanistan was killed Thursday, the U.S.-led coalition said Friday.

The incident took place in the Gulistan District of Farah province. Five other coalition and two Afghan soldiers were wounded.

Three U.S.-led troops southwest of Kabul in Wardak province were also killed Thursday.

Taliban militants have increased their attacks this year. The top U.S. commander in southeastern Afghanistan, Maj. Gen. Jeffrey Schloesser, said Tuesday that attacks on his troops were up 40 percent in the first five months of 2008.

U.S. Defense Secretary Robert Gates, asked about Schloesser's comments at a Thursday news conference, said one of the reasons for the increase was that more people are "coming across the border from the frontier area [he was referring to Pakistan]."

Gates said he hoped a newly announced Pakistani effort to clamp down on Islamic militants in the country's northwestern tribal districts would improve the situation in Afghanistan.

"The ability of the Taliban and other insurgents to cross that border and not being under any pressure from the Pakistani side of the border is clearly a concern," Gates said.

One of the weapons of choice for militants in Afghanistan is the roadside bomb.

Pentagon figures detailing the number of roadside bombs detonated and found in Afghanistan illustrate the level of insurgent activity.

In 2007, 876 roadside bombs blew up and 439 were found. This year 431 have blown up with 354 found.

The war in Afghanistan began after the al Qaeda terror network, harbored by the country's ruling Taliban regime, attacked New York and Washington on Sept. 11, 2001.


A U.S.-led invasion quickly toppled the Taliban regime.

Since then, the coalition and NATO-led troops have been battling a Taliban insurgency.