The police are frequently attacked in Afghanistan, and their training is part of measures the US and other international partners have identified as key to restoring stability in the country.
The main police building in Lashkar Gah, the administrative capital of Helmand, was attacked earlier this month and at least 11 people were killed.
New US strategy
Against this backdrop of rising violence, the US administration is expected to present a new strategy for its military operation in Afghanistan on March 31.
Barack Obama, the US president, is also about to appoint a new ambassador to the country.
Karl Eikenberry, nominated for the post, is an army general with considerable Afghan experience.
Formal procedures to confirm his appointment are to be held on Thursday.
The challenges that Eikenberry will face were highlighted by a report in the New York Times on Thursday, which cited American, Pakistani and other security officials as saying that operatives in Pakistan's military intelligence agency are aiding the Taliban’s campaign in southern Afghanistan.
"The support consists of money, military supplies and strategic planning guidance to Taliban commanders," the newspaper said.
"There is even evidence that ISI [Directorate for Inter-Services Intelligence] operatives meet regularly with Taliban commanders to discuss whether to intensify or scale back violence before the Afghan elections."
Hundreds of Taliban and al-Qaeda fighters sought refuge in Pakistan's northwest tribal region after the US-led invasion of Afghanistan toppled the Taliban government in late 2001.