A school caretaker, she lives with her husband in a middle-class district of east Baghdad with leafy avenues, satellite dishes and air-conditioning systems. But four hours out of six are without electricity. Their flat has few windows, to minimise the summer heat, and with no power there is no light, so the couple spend most of the day in gloom. "We can't really afford the kerosene so we try not to use the lamp much," Mrs Naief said. A power surge burnt the motor in their fridge and the oven does not work, so they cook non-perishable food on a stove on the floor. It has been this way since the invasion in March 2003. The caretaker's husband, Abdul Timimi, cursed the world in general and the Americans and Iraqi authorities in particular. "It's worse all the time."

All across the capital, in tones ranging from incandescent to resigned, there are similar stories of lives blighted by the blackouts. It is a jarring note to the optimism of last month's elections and bullish claims that the insurgency is faltering. Recent attacks on the gas and oil pipes to the power plants, officials say, show an increasingly sophisticated strategy of putting Baghdad under economic siege. Its six million inhabitants are accustomed to a near first-world infrastructure from Saddam Hussein's time and its degradation has fed antipathy to the occupation. After security, electricity is the priority and fixing it is a credibility test for the USbacked government.

"They think when they throw their light switches they know whether or not we are doing our job well," said Rick Whitaker, who administers infrastructure projects for the US Agency for International Development. Last month the national grid delivered half the 8,300 megawatts the country needed, so power was rationed, three hours on, three hours off, he said.

By summer, when 50C (122F) temperatures cook the city and everybody seeks air conditioning, the supply should rise to 6,500-7,000MW, close to the level under the Ba'athist regime, when managers and engineers could work with order and security.

The expected improvement reflected the efforts of the US and Iraqi authorities to rehabilitate old power plants and build new ones, said Mr Whitaker. The new system distributed power equitably across the country, unlike Saddam's, which starved the provinces to spoil the capital.

USAid alone was spending $2.4bn (£1.25bn) on infrastructure, but overall responsibility lay with the Iraqi government. Considering the dilapidation inherited two years ago - "power plants were held together by bailing wire and bubble gum" - Mr Whitaker said this was an unsung success.

Outside the heavily fortified green zone and its giant generators, the picture looks different. Residents say they are lucky to get four hours on, two hours off, and see no sign of improvement. Ahmed Sahib, 43, an electrician in the Karrada district, said he was besieged by clients, some tearful, begging him to work miracles. "Under Saddam we had 20 hours a day. That is what we are used to."

Booming demand for Chinese-made domestic generators, priced $145 to $450, has profited street traders like Ahmad Ghazi, just 17 and recently engaged thanks to his prospects as a long-term money-earner. Customers inspecting his wares expressed sympathy for those who could not afford generators. They said things were getting worse - disrupted supplies have made generator fuel scarce - and heaped blame on the Americans and Iraqi authorities. Some said it was a conspiracy to punish Iraqis.

It was precisely what the insurgents hoped to hear. To destabilise the new government and discredit the occupation, the disparate mix of Islamic radicals and former Ba'athists have focused their attacks on infrastructure on the pipelines to Baghdad's refineries and cut production of oil, kerosene and petrol.

The saboteurs had largely succeeded in isolating the city from power sources, the electricity minister, Aiham Alsammarae, told the New York Times this week. "They know what they are doing. Their intelligence is much better than the government's," he said.

A trip with engineers to a power plant under construction on the outskirts of Baghdad showed extreme security measures: three bodyguards for each engineer, armour-plated vehicles, and a helicopter for aerial cover. Six people died in an ambushed convoy in September.

The plant, which cannot be identified, was a virtual fortress: sandbags, concrete warrens, signs for mortar bunkers and Nepalese and Afrikaner guards. Security costs up to a quarter of the $160m budget, an official said. At least four Iraq contractors have been assassinated and many threatened. Managers praised the 600- strong workforce as brave, diligent and skilled. Lengthy security checks each morning shave three hours off what should be a 10-hour working day. Work on generators was several months behind schedule but by summer they should be producing 216MW, an engineer said. "We are making good progress but it's still not fast enough to get people the electricity they need."