“It’s critical. We need to do it as soon as possible,’’ said Amanda Williamson, a spokeswoman for the Red Cross. “The population really begins to suffer if they don’t have access to safe drinking water.’’

UN Secretary-General Kofi Annan said Monday that urgent measures should be taken to restore electricity and water to Basra. “I think a city that size cannot afford to go without electricity or water for long,’’ Annan said. “Apart from the water aspect, you can imagine what it does to sanitation. And so I think to that population.’’

The water supply in Basra, located in the southern part of the country, has been drastically reduced since a power outage there Friday.

Relief groups say the shortage of safe water could be extremely dangerous for the city’s nearly 1.5 million residents, leading to cholera, diarrhea, typhoid and other diseases. Children, the elderly and expectant mothers are particularly vulnerable.

Over the past few days, the Red Cross has worked with Basra officials to partially restore the water, rerouting water from the Tigris River. But they have been able to restore only enough water for about 40 percent of the city. And the quality of the water is not what it should be, say Red Cross officials. “It’s not a permanent solution by any means,’’ Williamson said.

Red Cross officials say they don’t know how the electrical system was damaged, but it shut down the water supply, which is linked to electrical grids. Basra has been the site of conflict in recent days.

Relief groups such as Oxfam of America, which specializes in water and sanitation systems, have raised concerns about attacks on critical facilities that serve civilian and military purposes. Oxfam officials say they have pressed both sides of the conflict to steer away from targeting power plants.

The shortage of clean water in Iraq was already dire before the US-led war, relief groups said.

Because of damage from the 1991 Gulf War, only half the water and sanitation systems in Iraq were operational, said Delaney, whose group did an assessment in December. He said about 500,000 tons of sewage was being dumped daily into fresh-water supplies.

Oxfam had estimated that prior to the war it would have taken a year or two to restore Iraq’s facilities to full capacity. “It is not known to what extent current hostilities have affected an already critical situation,’’ said Nathaniel Raymond, an Oxfam spokesman. Oxfam officials say they hope President George W. Bush’s request to Congress for emergency aid includes funding for such long-term projects.

Officials at the Red Cross, one of the only relief groups in Iraq, say they are still trying to figure out how to provide safe water to Basra residents.

Meanwhile, Oxfam and other relief groups are waiting for the war to end so they can help with water and sanitation expertise and supplies.

“We’re not sending any of our people in until the war is over and it’s seen as safe,’’ said Delaney, whose group has set up such systems in refugee camps in bordering countries. “We could only sit and watch at this point.’’