BEIRUT — Aid workers failed to evacuate anyone from blockaded rebel-held neighborhoods in the central Syrian city of Homs on Tuesday or deliver any food, increasing pressure on them to complete the ambitious humanitarian operation before a fragile truce expires, activists and Syrian Red Crescent officials said.
Over 1,000 civilians have already left the embattled districts, which have been under siege for 20 months by government forces and suffer from widespread hunger. The three-day truce that allowed the UN-Red Crescent operation was extended to six days, now to expire at midnight Wednesday.
But hundreds of civilians are still inside, and continued shelling and shooting between the two sides severely limited efforts.
Officials said Tuesday that they allowed over 100 men of fighting age to leave Monday after they were questioned and cleared of rebel links, state media said.
A UN spokesman however said that hundreds of others were held back for questioning and that they were concerned for their welfare.
Tuesday’s delay was for technical reasons, said Khaled Erksoussi, the head of operations at the Syrian Red Crescent. He said meetings between UN and Syrian officials in the city took more time than expected, forcing them to postpone all their activities until Wednesday.
‘‘There were no operations at all today. The UN and Red Crescent cars did not move,’’ Erksoussi said by telephone from Syria.
The holdup came after UN officials wrangled a hard-won extension of a three-day truce, which first went into effect Friday and which ended on Sunday evening, allowing for the evacuation of 1,130 civilians, mostly women, children, and the elderly, according to a tally by the international organization.
Food supplies were also delivered for 2,500 people inside the city, the UN estimated.
Syrian activists inside Homs blamed the government for the delay, saying it was to prevent the passage of food into rebel-held parts of the city.
‘‘The thugs, they are making obstacles, they don’t want assistance to enter,’’ said an activist who uses the nickname Abu Bilal.
There was no immediate comment from the Syrian government.
The operation came as Syrian opposition and government negotiators met in Geneva, holding their first face-to-face meeting this month as US and Russian officials prepared to join the stalemated talks.
The meeting broke up after three hours, and both sides said the session failed to produce an agreement even on the agenda. The UN mediator told reporters, ‘‘we are not making much progress.’’
Mediator Lakhdar Brahimi said there has to be ‘‘cooperation from both sides’’ and a ‘‘lot of support from outside.’’
Talks between President Bashar Assad’s government and the pro-Western opposition began last month, and then adjourned after a week. They resumed on Monday, following a 10-day break.
The government wants the talks to focus on fighting what it calls ‘‘terrorism.’’ The opposition wants to talk about a transition government to replace Assad.
Before evacuations began, authorities said that gunmen who surrendered would be allowed to return to normal life. In previous truces in other parts of Syria, some men have disappeared in detention facilities of Syrian intelligence after leaving blockaded areas, activists say.
In a statement Tuesday, the UN children’s agency said there were at least 500 children among those evacuated so far. UNICEF said the children were ‘‘terrified, frail, and emaciated.’’
“Mothers were anxious, and many were crying,’’ a statement from the UNICEF said. ‘‘All they wanted was for their children to reach safety.’’