Leon Panetta has arrived in Afghanistan after a US soldier shot dead 16 civilians

US Defense Secretary Leon Panetta has arrived in Afghanistan in a surprise visit after a NATO soldier shot dead 16 civilians.

According to the officials, Leon Panetta’s trip to Afghanistan was planned before 16 Afghan civilians were shot dead by an American soldier on Sunday.

Leon Panetta is due to have talks with President Hamid Karzai, provincial leaders and senior officials.

Correspondents say his visit has taken on a new meaning as political pressure mounts on Afghan and US officials over the unpopular war.

Leon Panetta is also due to speak with US troops in Afghanistan as fears mount that they could be the victims of a Taliban-led backlash over the killings of villagers, including nine children, by the rogue US soldier.

His arrival at Bastion Airfield in Helmand province came a day after protests over the massacre flared in the eastern city of Jalalabad.

Leon Panetta is the most senior US official to visit Afghanistan since the shootings.

He told reporters ahead of his trip that he believed that American strategy in Afghanistan was working and would withstand repercussions from the killings.

“I think we’re on the right path now and what we’ve got to do is convince people that despite these kinds of events we ought not to allow [them] to undermine that strategy,” Leon Panetta said on Monday.

“It’s important that we push on, and that we bring this war to a responsible end and achieve the mission that all of us are embarked on,” he said.

Leon Panetta’s trip coincides with discussions in the US between UK Prime Minster David Cameron and President Barack Obama over a possible “endgame” to the war in Afghanistan.

The leaders are expected to agree that Afghan forces should take over a lead combat role by mid-2013 – earlier than planned – but the US president has said there will be no “rush for the exits”.

Correspondents say that anti-Americanism was rampant in Afghanistan even before the shootings.

Last month there was outrage over US troops inadvertently burning Korans on an American base.

Fury also followed the posting of a video on the internet in January apparently showing four US marines urinating on Taliban corpses.