In a speech in Riyadh before diplomats, Turki said US-led NATO troops had irrevocably alienated the Afghan people and had no hope of rebuilding the country.
"What Afghanistan needs now is a shift from nation-building to effectively countering terrorists," Turki told the Arab News conference.
US President Barack Obama "should not be misdirected into believing that he can fix Afghanistan's ills by military means."
"Hunt down the terrorists on both sides of the Afghan-Pakistan border, arrest them or kill them, and get out, and let the Afghan people deal with their problems.
"As long as GI boots remain on Afghan soil, they remain targets of resistance for the Afghan people and ideological mercenaries."
Turki, who has long served a central role in Saudi-Afghan relations, scolded Washington's handling of relations with Kabul.
"The inept way in which this administration has dealt with President (Hamid) Karzai beggars disbelief and amazement.
"Both sides are now filled with resentment and a sour taste in their mouths," he said. "How can they both get out of that situation? I don't know."
The chairman of the King Faisal Center For Research and Islamic Studies, Turki has no official position but is believed to often reflect high level thinking in the Saudi government.
He is the brother of Foreign Minister Prince Saud al-Faisal, and analysts speculate he could become foreign minister when Saud retires.
Turki said Arab states have given Washington four months to show progress in US-guided Palestinian-Israeli peace talks.
"The Arab world has given Obama until September to get things done," said Turki.
"It is not enough to talk the talk. He has to walk the walk.
"If he does not succeed... then I (will) ask President Obama to do the morally decent gesture and recognise the Palestinian state that he so ardently wishes to exist.
"He can then pack up and leave us in peace and let the Palestinians, Syrians and Lebanese negotiate directly with the Israelis. No more platitudes and good wishes and visions, please."
Turki also faulted the US and European approach in trying to halt Iran's alleged efforts to build a nuclear weapon.
"The discussions on Iran's nuclear ambitions started off on the wrong foot. The carrot and stick approach does not work," he said.
For one, he said, the US and Europe have had double-standards in dealing with Iran on the one hand, and other nuclear countries on the other.
"You cannot ask Iran to play on one level while you allow Israel, India, Pakistan, and North Korea to play on other levels."
Turki said a successful strategy toward Iran requires even-handedness, a "universal nuclear security umbrella" for the countries in the area, and "a good military option" against any regional country which does not cooperate.
He said Clinton had undermined efforts to move toward a regional nuclear-free zone, after the UN Security Council's five permanent members recently expressed support for the idea.
"Alas... Clinton then voided the issue of its value by stating that the conditions do not yet exist for establishing the zone," he said.
"Why, then, did she join the other members of the P5 in issuing their statement?"
Turki said he hoped Obama "will find the way to correct his secretary of state's nullification of making our area free of weapons of mass destruction."
Turki also warned of rising violence in Iraq after the pullout of US troops next year, warning both internal and external groups seek to carve up the country.
"Imagine what will happen once internal strife and fighting escalates" following the US pullout, he said.
Without a UN Security Council effort to protect Iraq's current borders, the consequence could be "regional conflict on a scale not seen since the Ottoman-Safavid wars of the 17th and 18th centuries," he warned.
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