Cameron Munter, the US ambassador to Serbia, called for the Serbian government to guarantee the safety of foreign diplomatic missions and their personnel.
The US withdrew family members and non-emergency personnel from its embassy in Belgrade on Friday.
Rioters set the embassy's outer office on fire on Thursday night and broke several windows before police chased them away. One rioter was killed.
A number of other embassies were also damaged and on Friday EU officials warned the violence could impact EU-Serbian ties.
But calm had returned to Belgrade on Friday, as Serb police guarded the embassies damaged in the rioting.
Al Jazeera's Barnaby Phillips reported that a heavy clean-up operation was under way, clearing debris from Belgrade's streets amid the normal morning rush-hour traffic.
Russia, which has refused top recognise Kosovo as Europe's newest nation, blamed supporters of Kosovo's independence for triggering the embassy attacks.
But Javier Solana, the EU's foreign policy chief, said continued violence would stall talks on Serbia's inclusion into the union.
Solana said on Friday: "These acts of violence lead nowhere and they cannot help anybody."
He said that negotiations on an agreement designed to prepare Serbia for eventual EU membership would have to wait until things "calm down".
|Several stores were cleaned out by looters,|
leaving display windows completely bare [AFP]
Solana said: "The embassies have to be protected, that's the obligation of a country."
Solana is in Brdo Pri Kranju, Slovenia, for a meeting of EU defence ministers.
On Thursday, the UN Security Council condemned "in the strongest terms the mob attacks against embassies in Belgrade" and said that it welcomed the steps taken by the Serbian authorities to restore order and protect diplomatic property and personnel.
Zalmay Khalilzad, the US ambassador to the UN, had said he was "outraged" by the attack.
The Croatian embassy was also attacked in Thursday's rioting, and a residential building next door was damaged by flames.
After breaking up the protests, riot police fought running battles in Belgrade's central area, while dozens of looters broke into shops following a state-sponsored demonstration against Kosovo's independence in which nearly 200,000 people took part.
It was the worst rioting in Belgrade since 2000, when pro-democracy protesters confronted the security forces of Slobodan Milosevic, the Communist-era leader, in an uprising that led to his removal.
Belgrade's emergency centre said 96 people, a third of them police, had been treated for light injuries in the night. There were more than 100 arrests, police said.