Kabul ? A roadside bomb killed two U.S. service members in southern Afghanistan on Saturday as the country’s top NATO commander acknowledged an increased risk to foreign troops will accompany an influx of reinforcements aimed at routing the Taliban.

The deaths brought to at least 22 the number of American service members killed so far this month — compared with only 14 for the whole of January last year. A mild winter has brought no respite to the fighting, which traditionally drops off during the cold months.