An American service member died in a bomb blast in Afghanistan on Friday, making August the deadliest month of the eight-year war for U.S. forces.

The service member's vehicle struck a roadside bomb in the east, NATO forces said. U.S. forces spokeswoman Capt. Elizabeth Mathias confirmed the nationality but did not provide further details.

The death brings to 45 the number of U.S. troops who have died in Afghanistan this month, surpassing the 44 troops killed in July, which had been the deadliest.

More than 60,000 U.S. troops are in Afghanistan to fight rising insurgent violence, boosted by about 21,000 pouring in this summer as part of President Barack Obama's effort to rout the resurgent Taliban and increase security for presidential elections held last week.

Attacks typically rise in Afghanistan during the summer and U.S. officials had warned that violence was likely to increase along with the troop surge. Roadside bombings have skyrocketed as U.S. troops move into areas where insurgents have been entrenched for years.

The increased military presence and the political tension surrounding this month's presidential election have strained U.S.-Afghan relations.

President Hamid Karzai has angrily accused the U.S. of pushing for a runoff vote during a heated meeting with the special envoy to the region, according to officials familiar with the encounter.

The verbal exchange occurred the day after the Aug. 20 vote during a meeting in Kabul between Karzai and U.S. special envoy Richard Holbrooke, according to two officials who were briefed about the meeting. They spoke on condition of anonymity because of the sensitivity of the information.

Karzai assured Holbrooke he would accept the election results but bristled when the envoy asked if he would also agree to a runoff if none of the 36 candidates won more than 50 percent, the U.S. officials said.

An angry Karzai accused the U.S. of pushing the idea of a second round even before all votes had been counted. He said would accept the election commission's tabulation as long as it reflected the facts. He did not elaborate.

Final results are due next month but partial figures released this week show Karzai leading former Foreign Minister Abdullah Abdullah and 34 other candidates but falling short of the 50 percent mark needed to avoid a runoff.

The U.S. Embassy confirmed the Aug. 21 meeting and said the two discussed the election but would not go into details.

"There was no shouting and no one stormed out," said Caitlin Hayden, an embassy spokeswoman. She noted Holbrooke and Karzai met again a few days later. Karzai spokesman Humayun Hamidzada also confirmed the meeting but gave no further details.

Tension in U.S.-Afghan relations emerged after President Barack Obama's administration took office this year. Karzai enjoyed close ties with the Bush administration, which helped propel him to power after the collapse of the Taliban government in the 2001 U.S.-led invasion.

U.S. officials have accused Karzai of weak leadership in the face of the resurgent Taliban, corruption, and allowing the flourishing drug trade. However, the U.S. has insisted it is neutral in the election and will work with whoever wins.

The New York Times reported this week that the Obama administration is alarmed at the prospect that Karzai's running mate, Mohammad Qasim Fahim, may be linked to the drug trade.

Quoting an unidentified administration official, the newspaper said if Fahim becomes vice president, the U.S. would likely consider imposing sanctions such as refusing him a U.S. visa or going after his personal finances.

A U.S. official in Washington confirmed the essence of the report, saying there were "a number of individuals" whom the U.S. would not like to see in a future Afghan government. The official said the U.S. had conveyed those sentiments to the Afghan government. He spoke on condition of anonymity because of the sensitive subject matter.

Relations between the Americans and Afghans have also been strained by the U.S. policy of detaining suspected insurgents without charge and killing civilians in military operations. The new U.S. commander, Gen. Stanley McChrystal, has issued new orders sharply limiting use of airstrikes and encouraging U.S. troops to protect civilians.

Nevertheless, friction persists.

On Friday, an Afghan lawmaker accused the U.S. military of violating Islamic and international law two days before by using a helicopter gunship to fire on a medical clinic where an injured Taliban commander had bunkered down. The U.S. military said it cleared the clinic of civilians and government officials approved the use of the helicopter to end the firefight.

After the battle, Afghan and U.S. forces met with villagers and discussed rebuilding the clinic, a U.S. summary of the meeting said. The wounded Taliban commander was taken prisoner.

"There must have been another way or tactic to use to get to him without destroying the hospital," said lawmaker Khalid Faroqi, calling the action "an offense."

Human rights group Amnesty International has urged NATO forces to investigate the attack, saying the military alliance may have violated international laws of war that protect wounded fighters getting medical aid.

Afghanistan's health minister said insurgents violated the sanctity of the clinic by bringing their guns inside. They hid the weapons under their clothes and were the first to fire, he said.

Also Friday, militants ambushed a police convoy in central Ghazni province, killing three policemen and wounding 28, said Abdul Karim, a police official.