Insurgents have attacked Nato forces in eastern Afghanistan.
Several attackers were killed in the Taliban attack on a base at an airfield outside Jalalabad, near the border with Pakistan.
Gunmen set off a car bomb and fired rocket-propelled grenades, and wounding two soldiers, Nato said.
Gen Petraeus, who is set to take over command of the US military in Afghanistan, also warned that fighting “may get more intense in the next few months”.
He is expected to take up his post as Nato commander in Afghanistan following the dramatic departure of Gen Stanley McChrystal last week.
The attack began at 0730 local time (0330 BST), with insurgents attacking the airport from different directions.
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BBC News, Kabul
The attack on the military base near Jalalabad airport was planned and co-ordinated, a sign that after nine years of fighting in Afghanistan, the Taliban still have plenty of fight in them, and are growing more sophisticated as the war goes on.
The base is shared by Afghan and international troops, and Afghans, say Isaf, are increasingly taking lead in protecting the area, and attacking insurgents.
A Nato spokesman said the perimeter of the base was not breached.
An Afghan soldier and one international service member were wounded.
A Taliban spokesman, Zabiullah Mujahid, said six suicide attackers had taken part in the assault.
Eight insurgents died in the ensuing gun battles, the Associated Press news agency reported.
The attack is yet another example of the increasingly sophisticated assaults favoured by the Taliban, says the BBC’s Quentin Sommerville in Kabul.
These commando-style operations are increasing in numbers, and often result in higher civilian and military casualties.
A total of 100 Nato troops serving in Afghanistan were killed in June, making it the deadliest month for the alliance since the US-led invasion of 2001.
An Afghan army-led operation is taking place in nearby Kunar, where 600 troops are attempting to rout about 250 insurgents thought to have links to al-Qaeda.
Jalalabad is one of Nato’s largest bases in Afghanistan, after Kandahar in the south and Bagram near Kabul.
Both of those bases have been attacked by insurgents in recent months.