By Alphonso Toweh
MONROVIA, Feb 23 (Reuters) - The United States wants to help war-shattered Liberia by rebuilding its infrastructure and returning mains electricity to its crumbling cities, a senior U.S. legislator said on Thursday.

House Democratic Leader Nancy Pelosi, leading an 11-member U.S. House of Representatives team, hailed President Ellen Johnson-Sirleaf's election as Africa's first elected woman head of state as a move toward stability after a 14-year civil war.

"The election of the president electrified the world. Now we are going to electrify Liberia by turning on the lights, building infrastructure and helping the economy grow," Pelosi, a Californian Democrat, said after meeting Johnson-Sirleaf.

The United States spent more than $840 million over the last year in Liberia, whose capital Monrovia is still without running water or mains electricity almost three years after the war to oust warlord-turned-president Charles Taylor ended.

Liberia, Africa's oldest republic, was founded by freed American slaves in 1847. Liberians have traditionally looked to the United States as a role model and many emigrated to the country during the war, which killed 250,000 people.

"We have an obligation and responsibility to help Liberia, to reward the democratic elections and encourage peace," Pelosi said.

Campaiging on a pledge to restore Liberia to its former prosperity, Johnson-Sirleaf defeated soccer millionaire George Weah in a presidential run-off in November.

"The United States has supported us in the transitional period to peace," said Johnson-Sirleaf, a former World Bank economist. "They have sent a signal that has enabled us to mobilise support from some of external partners."

The U.S. legislators are also visiting Sudan, Cape Verde, Ghana and South Africa during their tour.