"Frankly, I hope there will be more troop contributions and there needs to be more Afghan forces," Rice told reporters travelling with her on the flight from London.
Rice, speaking against the backdrop of a NATO defence ministers' meeting in Lithuania, said alliance members needed to "come together to give enough military power to do what needs to be done on the front end of the counter-insurgency effort".
After flying into the Afghan capital Kabul, Rice and Miliband travelled in a U.S. military plane to a sprawling base in the southern city of Kandahar, the birthplace of the Taliban and the main city in Afghanistan's most volatile region.
"Kandahar does have an iconic status in the history and position of Afghanistan," said Miliband. "I hope we will be able to take a message in what is really a new drive, a new phase in terms of counter-insurgency."
Rice and Miliband planned to meet NATO commanders in the frontline of the fight against the Taliban.
The United States and Britain have been urging other NATO members to share more of the combat burden in southern Afghanistan where the Taliban insurgency is strongest.
Some NATO countries have bristled at public criticism from Washington over the refusal of a number of alliance members to position their forces in the more dangerous south.
Germany, for example, under its parliamentary mandate can send only 3,500 soldiers to the less dangerous north as part of the 42,000-strong NATO mission.
That means most of the fighting against the Taliban is shouldered by Canada, Britain, the United States and the Netherlands. They all want others to contribute more.
