(Corrects "question" to "quest" in second paragraph)

*Leaders to meet again after August poll

*Kerry sees "reality" in leaders' views (Adds Karzai, Zardari comments, details)

WASHINGTON, May 7 (Reuters) - The United States, Afghanistan and Pakistan will hold a trilateral summit after the Afghan presidential election in August, the special U.S. envoy for the region said on Thursday, citing progress in getting often fractious American allies to work together.

"I hope the American public sees that we're making progress in the quest for real cooperation between Afghanistan and Pakistan, because without that cooperation, success is not achievable," envoy Richard Holbrooke told reporters after a meeting with Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari.

The two South Asian leaders on the frontline of the fight against Islamic extremism met with the Senate Foreign Relations Committee, a day after they promised President Barack Obama to work together to defeat al Qaeda and the Taliban.

Karzai and Zardari came to Washington amid heavy criticism of their efforts to combat a Taliban resurgence in their countries.

John Kerry, chairman of the committee, praised the two leaders for candidly answering U.S. lawmakers' sharp questions about the war, now in its seventh year in Afghanistan.

"All of the Senators who were present today were encouraged by the reality with which both presidents addressed the questions and summarized the challenge," Kerry told reporters.

Karzai, who is up for reelection in August, said the talks "brought us to the right light of mind on questions that we have together" and pledged closer cooperation.

Zardari said the meeting with senators who play a key role in overseeing U.S. aid to his country and Afghanistan "brings strength to the situation that we have and anything that brings strength is very good."

Obama announced a new approach to the fight against al Qaeda in both countries in late March, offering more aid but also more than 20,000 extra troops to Afghanistan this year.

(Reporting by Paul Eckert, Editing by Sandra Maler and Paul Simao)

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