The US says all 32 countries in the multinational force in Iraq have agreed not to give in to the demands of hostage-takers.
Four Jordanian men were freed but the fate of three others is unclear
"We are united in our resolve to make no concessions to terrorists," the state department announced.
This is a clear message to militants that seizing foreigners to put pressure on governments to withdraw their troops will not work, correspondents say.
Six Jordanian and Turkish hostages were released earlier on Wednesday.
The US announcement came as UN Secretary General Kofi Annan said the force would be used to guard UN personnel and property when they returned later in August.
Staff were withdrawn last year after two suicide bomb attacks on their headquarters.
About 20 other foreign nationals are still being held captive in Iraq.
There has been a dramatic upsurge in kidnapping in recent weeks as militants try to exert emotional pressure on foreign governments to pull out, and on overseas companies to stop doing business in Iraq.
While several private firms have agreed deals to secure the release of their employees, the US said countries in the multinational force would not yield.
State department spokesman Richard Boucher said the idea for a common policy statement on hostage-taking was first proposed by Bulgaria.
The US had then followed it up with each of the other governments in the multinational force and reached an agreed principle to be expressed by individual nations in their own words.
The co-ordinated campaign aims to signal to terror groups that there would be no "weakening of resolve", the US statement read by Mr Boucher said.
Countries with troops in Iraq or whose nationals have been working for companies supplying the US military have been particular targets.
As well as sending a clear message to militants, it is also a response to the Philippines which withdrew its own troops early to ensure the safe release of one of its nationals, says the BBC's Jill McGivering in Washington.
That move angered the US and increased pressure on other members of the multinational force facing similar demands, she reports.
"We are committed to making sure that the perpetrators of terrorists acts against our citizens and soldiers are brought to justice," the US statement said.
"We understand that conceding to terrorists will only endanger all members of the multinational force, as well as other countries who are contributing to Iraqi construction and humanitarian assistance," it said.
Hostage house 'raided'
Meanwhile, four Jordanian lorry drivers have been freed in Falluja, apparently after a group of Iraqis stormed the place where they were being held and set them free.
Two Turkish drivers, Abdulrrahman Demir and Said Unurlu , were also released by militants from Tawhid And Jihad who said their haulage firm had agreed to stop work in Iraq.
Some believe the Philippines troop pullout set a dangerous precedent
Tawhid And Jihad earlier announced it had shot dead another Turkish lorry driver, Murat Yuce.
The four Jordanians have been named as Ahmad Abu Jaafar, Mohammad Ahmad Khleifat, Khaled Ibrahim Masoud and businessman Ahmad Tayseer Sunokrot.
One of the hostages told Reuters news agency by telephone that local people had raided the house where they were being held.
Their captors had called on the people of Jordan to force their government to end support for the new government in Baghdad.
A company which employs two of the men also pledged to halt operations in Iraq - another demand of the kidnappers.
There are no details about the fate of three remaining Jordanian captives being held by a group calling itself "The Mujahideen of Iraq, the Group of Death".
Lorry routes from Jordan and Turkey are vital supply lines for Iraq.
The multinational force is:
Albania, Australia, Azerbaijan, Bulgaria, Czech Republic, Denmark, El Salvador, Estonia, Georgia, Hungary, Italy, Japan, Kazakhstan, South Korea, Lativa, Lithuania, Macedonia, Moldova, Mongolia, Netherlands, New Zealand, Norway, Poland, Portugal, Romania, Singapore, Slovakia, Thailand, Tonga, Ukraine, UK, US