A top US commander says Iraqi fighters in Falluja have "days not weeks" to hand over their weapons otherwise US forces will renew their offensive.
Iraqis at the funerals in Basra vented their rage
Lt Gen James Conway said his force of about 1,500 marines continued to stop what he says are about 200 foreign fighters, from escaping.
There has been more fighting in the town, west of Baghdad, after a battle on Wednesday left 39 Iraqis dead.
In Basra families mourned, the day after blasts killed at least 68 people.
Wednesday's suicide bombings at three police stations in Basra and at the police academy in the nearby town of Zubair were the
bloodiest attacks yet in the British-controlled zone.
Hundreds of Iraqis took to the streets of Basra to protest against the attacks and shout anti-coalition slogans.
'We are not pleased'
About 1,000 American soldiers are being sent to Falluja as reinforcements.
Tens of thousands of Falluja's residents fled the city after fighting broke out on 5 April.
Gen Conway, commander of the 1st Marine Expeditionary Force based in western Iraq, said the response to a truce between US forces and Falluja civic leaders had been disappointing.
He questioned whether the Iraqi peace negotiators could persuade the guerrillas in Falluja to hand over weapons.
"We have had reservations regarding their ability to peacefully influence because it is the other guys who have the weapons," he said.
Jennifer Glass, reporting for the BBC at Marine Headquarters outside Falluja, says US officials were hoping that modern guns and heavy weapons would be turned in to show insurgents were serious about finding a peaceful solution.
But Gen Conway said: "We are not pleased at all with the turnover that we saw yesterday. The volume probably amounted to a pick-up truck [full of weapons]."
He added: "It's days not weeks. The cordon cannot continue forever. If the negotiators don't deliver a peaceful scenario we're going to do what we came here to do."
The Americans have been demanding the surrender of the killers of four American security contractors in the city at the end of March as well as the handover of heavy weapons there.
Unofficial Iraqi sources estimate that up to 600 people have been killed during the siege of the Sunni Muslim city of 300,000 while the US military has lost scores of troops in the region.
Correspondents in Falluja say some families and local Iraqi police officers forced out by the fighting have now begun trickling back into the city.
America's top soldier, Gen Richard Myers, has said Falluja had to be "dealt with".
"We went in because we had to find the perpetrators and what we found was a huge rat's nest that is still festering today," the chairman of the Joint Chiefs of Staff said.