The ranking Republican on the US Senate Armed Services Committee said Nato and Afghan troops will prevail in the war if they can succeed in securing and bolstering governance in the Taliban stronghold of Kandahar.

Sen. John McCain, who visited Afghanistan's largest city in the south on Monday with two other US lawmakers, warned of tough fighting ahead and predicted that casualties would rise in the short-term.

"The Taliban know that Kandahar is the key to succes or failure," McCain told a news conferenceattheairportin Kabul.