"I think we'll have to see," department spokesman Richard Boucher told reporters when asked whether bilateral relations would be affected by the Philippine decision.
On Wednesday, a Philippine official in Baghdad said truck driver Angelo de la Cruz, who had been threatened with execution, was "safe and there is no more risk of him being executed".
Earlier, a purported Iraqi group calling itself the Khalid Ibn al-Walid Brigade threatened to behead de la Cruz by Tuesday unless Manila caved in to their demands for total troop withdrawal by 20 July.
The unconfirmed release of de la Cruz may have come as a result of fierce 11th-hour negotiating between his captors and Philippine delegates in Iraq.
On 13 July, Philippines Deputy Foreign Minister Rafael Sequis said in a statement broadcast on Aljazeera that his government would submit to the captors' demands.
"We are responding to your request and are to withdraw our humanitarian contingent in Iraq as soon as possible," Sequis said.
Philippine Foreign Secretary Delia Albert confirmed on Wednesday that Manila had started pulling its troops out of Iraq, suggesting eight members of the 51-member contingent had already left the war-torn country.
The proposal to withdraw Manila's
troops has irked Washington
Washington considers Manila's offer of early troop withdrawal as running contrary to US policy and "giving in to terrorist demands".
Nevertheless, Boucher said Manila had stood beside the US "as a friend and an ally on many, many occasions in the decades past, and so we look forward to continuing to work with the Philippines in all the areas where we can productively do that."
Asked to elaborate on a possible review of US links with the Philippines, a US government official, speaking on condition of anonymity, said: "It's hard to speculate at this point."
"There is no indication of a change in policy across the board on cooperation in fighting terrorism," he said.
The Philippines, facing a terrorism threat at its own backyard, was among the first to support the so-called US-led global war on terrorism after the September 11 2001 attacks in the US.
Among other forms of assistance, the US grants financial and military aid to the Philippines, which was given the non-NATO ally status by Washington last year to highlight their close defence links.
Filipinos called on their leaders
to pull troops from Iraq
The US military also helps train Philippine soldiers battling the al-Qaida-linked Abu Sayyaf terror group in the country's troubled south.
Boucher noted that the US and the Philippines had pledged to continue the strong cooperation they have had in counterterrorism.
"We have worked closely with them on many other things around the world, in terms of sharing information, law enforcement information, training, a lot of different forms of cooperation - all of which we certainly would like to continue," he said.