WASHINGTON (Reuters) - The United States must increase its economic and social aid to Afghanistan as part of its effort to combat surging Taliban militants, a senior Obama administration official said on Thursday.

Outlining President Barack Obama's strategy to fight terrorism beyond military action, his counterterrorism adviser John Brennan pointed to the need to help Afghanistan through its upcoming elections and boost economic support.

"This means a dramatic increase in our development efforts -- working with the government to end corruption, improve the delivery of basic services and build an economy that isn't dominated by drugs," Brennan said at the Center for Strategic and International Studies think tank.

He said that economic support would "help restore people's hope in the political process and in legitimate institutions." He also noted that failing to build political and social institutions helped extremists recruit more followers.

Brennan offered no specifics about how much additional foreign aid should go to Afghanistan. In June, the U.S. Congress approved roughly $1 billion in aid for economic development, agricultural programs, strengthening national and provincial governance and expanding the rule of law.

Since the U.S.-led invasion in 2001, Washington has tried to help Afghanistan stand up a government and infrastructure that would counter the Taliban militants who previously governed the country and have surged in recent months.

Afghans go to the polls on August 20 to elect a president. Taliban forces have vowed to disrupt the vote. NATO-led and Afghan forces have said they are ready to secure polling centers.

(Reporting by Jeremy Pelofsky, editing by Will Dunham)