The US and UK have criticised a deal made with the Taleban by Italy and Afghanistan to secure the release of a kidnapped Italian journalist.
Daniele Mastrogiacomo was released on Monday
They say the release of five militants in exchange for Daniele Mastrogiacomo, who was freed on Monday, endangered Nato troops and encouraged kidnappings.
The deal has sparked a row in Italy, which has some 1,800 troops stationed in the country.
The Afghan translator working with Mr Mastrogiacomo is still being held.
US and UK officials, speaking on condition of anonymity, said the swap increased the risk of similar kidnappings of Nato and Afghan troops.
"The UK has serious concerns about the implications of releasing Taleban in return for hostages," a UK Foreign Office spokeswoman said.
"This sends the wrong signal to prospective hostage-takers."
Washington has formally complained to Rome over the exchange, adding the deal "caught the US by surprise", a senior US administration official said.
"It is US policy to use every appropriate resource to gain the safe return of hostages, but to make no concessions to individuals of groups holding those hostages," she said, adding that the US "did not and do not approve of concessions to terrorists".
On Wednesday, the move was also condemned by Dutch Foreign Minister Maxime Verhagen during a visit to the Afghan capital, Kabul.
"When we create situations where you can buy the freedom of Taleban fighters when you catch a journalist, in the short term there will be no journalists any more," he said.
The Afghan government has defended the move as "exceptional", carried out because of Italy's relationship with Afghanistan.
On Wednesday, journalists' groups called for the release of translator Adjmal Nasqhbandi who was seized with Mr Mastrogiacomo three weeks ago.