US Defence Secretary Robert Gates has arrived in the Afghan capital, Kabul, on a surprise visit.

美国国防部长罗伯特·盖茨突然抵达阿富汗首都喀布尔进行访问。

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Mr Gates's visit has been overshadowed by last week's civilian deaths
He is due to meet Afghan President Hamid Karzai, US troops and allied² commanders during his two-day visit.

Later this month, Mr Karzai is due to announce the schedule for the start of the handover of security responsibility from foreign forces to Afghans.

The visit comes at a time when Kabul's ties with the US are strained over the issue of civilian killings⁴.

On Sunday, President Karzai told Gen David Petraeus, the US commander of foreign troops in Afghanistan, that his apology for the deaths of nine children in an air strike was "not enough".

The children were killed in a Nato strike on Tuesday.

"This is not a decision-making trip," news agency AFP quoted Geoff Morrell, Mr Gates's press secretary, as saying.

"We are going to go south, we are going to go east, and he will come away from this visit hopefully with a better sense of how far we've come in the past three months," he said.

The Obama administration has said it will begin withdrawing US troops from Afghanistan in July and the exercise will be complete by 2014.

But Mr Gates is yet to indicate how many of the 97,000 US forces in the country will be withdrawn⁵.

The issue of civilian casualties is a source of widespread public anger and of tension between the Afghan government and the US.

Hundreds of people rallied on Sunday to denounce（谴责，告发） the killing³ of civilians⁶.

The protesters condemned⁷ both Nato and the Taliban for killing civilians.