US troops could be more involved in Kandahar
The US has said it is planning a new offensive later this year to drive the Taliban from the southern Afghanistan city of Kandahar.
The current action against the Taliban stronghold of Marjah was a "prelude" to a bigger operation, a US official said.
The US general in charge of Nato forces in Afghanistan has said the local population in Kandahar is at risk.
Kandahar is Afghanistan's second largest city, and was once a Taliban stronghold.
A major offensive there would follow the current military operation in neighbouring Helmand province.
"If the goal in Afghanistan is to reverse the momentum of the Taliban... then we think we have to get to Kandahar this year," an official in the White House told reporters.
The US goal was to bring "comprehensive population security" to the city.
Suicide attacks are frequently carried out in Kandahar, with one at the beginning on February killing three people.
He described Marjah as "a tactical prelude to a comprehensive operation in Kandahar City."
The Marjah offensive by Nato forces began in mid-February, and has several more weeks to go.
It was "pretty much on track", the official said.
In Kabul on Friday, explosions and shooting took place in an area of hotels and guesthouses popular with foreigners. Up to nine Indians, a Frenchman and an Italian were killed.
Three gunmen and two policemen died in a gun battle that lasted several hours. Taliban militants said they had carried it out.
President Hamid Karzai condemned the violence. India called it "barbaric".
Kabul has been relatively quiet since 18 January, when Taliban bombers and gunmen attacked government targets and shopping malls, killing 12 people.
Friday's attack is also the Taliban's first major raid since the arrest of key leader Mullah Abdul Ghani Baradar in Pakistan this month.