The US's two most senior defence officials made separate visits to Afghanistan and Pakistan yesterday marking the mounting concern in Washington about extremist havens in the ungoverned border areas.

Robert Gates, US defence secretary, arrived in Afghanistan where violence has intensified this year as Taliban and al-Qaeda militants step up attacks on US, Afghan and Nato forces. The Pentagon plans to send more troops to Afghanistan next year to counter violence which is at its highest level since the 2001 invasion.