The international military strategy in Afghanistan must not be derailed by the massacre of Afghan civilians by a US solider, political leaders said.
The Prime Minister David Cameron, who flies out to Washington on Tuesday for talks with President Barack Obama, described the killings as "an absolutely dreadful event", but insisted Britain and its allies would "stick to the plan".
"We must stick to the plan and deliver the plan as we set it out," he told reporters in Downing Street.
"This really is an absolutely appalling thing that has taken place and, of course, it will have its impact, but we must do everything we can to make sure it doesn't in any way derail the very good work that American and British and other Isaf forces are doing in Afghanistan."
The White House echoed Mr Cameron's commitment to the mission in Afghanistan. A spokesman said: "The focus of our overall strategy is not in reaction to a single event. I do not believe that this incident will change the timetable of a strategy that was designed and is being implemented in a way to allow for the withdrawal of U.S. forces, to allow for the transfer of lead security authority over to the Afghans."
President Obama personally called Afghanistan's President Karzai to express his "shock and sadness" at reported killing of Afghan civilians.
He has also expressed concern for the safety of US personnel in Afghanistan since the incident.
The Taliban was quick to exploit local anger over the deaths of the 16 Afghans - many of them children - vowing to seek revenge for the "blood-soaked and inhumane crime".
A US Army staff sergeant is currently in custody at a Nato base after reportedly handing himself in following the attacks in two villages near his base in Kandahar province.
The US military authorities have promised a "rapid and thorough investigation" into the killings which have become the latest setback to hit the international military force in the country (Isaf).
Former head of the Army, General Lord Dannatt, backed David Cameron's plan to continue with the military strategy.
He told BBC News: "If we were to pull the plug and scuttle and run now we would not be able to complete that process of handing over to the Afghans and we would undoubtedly prejudice all the good work we have done over the years at considerable cost in both blood and treasure."