Hillary Clinton Wednesday bade farewell to her NATO allies after making her last appearance as U.S. Secretary of State here, praising the military alliance for having made "great strides".

"I've spent a bit of my time in this building over the past four years, and I think it was time well spent," Clinton mused, speaking after two days of talks among the 28-member alliance in Brussels.

U.S. Secretary of State Hillary Clinton called Wednesday for an open and transparent dialogue in Egypt amid a deepening political crisis over sweeping powers adopted by President Mohamed Morsi.

"The upheaval we are seeing now once again in the streets of Cairo and other cities indicates that dialogue is urgently needed," Clinton told journalists at the end of a two-day NATO foreign ministers meeting in Brussels.

Iran said on Tuesday it captured a small U.S. drone that penetrated its airspace over Gulf waters, but the White House and the U.S. Navy in the region denied the report.

The naval arm of the Iranian Revolutionary Guards said in a statement on the Guards website Sepahnews.com that "the unmanned U.S. drone patrolling Persian Gulf waters, performing reconnaissance and gathering intel, was captured as soon as it entered Iranian airspace."

Syria has begun mixing chemicals that can be used to make deadly sarin gas, a U.S. official told AFP Monday, amid fears that President Bashar Assad's forces could attack rebels with chemical weapons.

"We've picked up several indications which lead us to believe that they're combining chemical precursors," the official said, on condition of anonymity, adding that the operation was apparently aimed at making sarin.

China on Monday branded a U.S.-Japan security treaty "a product of the Cold War" after Washington reaffirmed its commitment to Japan in its territorial dispute with China over the Senkaku Islands, known in Chinese as the Diaoyus.

The amendment, attached to the National Defense Authorization Bill, noted that while the United States "takes no position" on the ultimate sovereignty of the territory, it "acknowledges the administration of Japan over the Senkaku Islands".

Even if NATO foreign ministers approve Turkey's request to deploy Patriot missiles on the border with Syria as expected, it will still take some weeks to get them in place, a top U.S. official said Monday.

The United States was "hopeful that NATO will be in a position to respond positively and agree to help Turkey bolster its air defences," a senior State Department official said.

The U.S. and Chinese militaries on Friday wrapped up a modest disaster-relief exercise hailed as a tentative trust-building step amid growing suspicions between the Asia-Pacific region's largest armed forces.

While not a full-fledged operation, the two-day exercise at People's Liberation Army barracks outside the city of Chengdu consisted of U.S. and Chinese officers sitting around a table facing a flat-panel video screen and discussing how they would respond to an earthquake in a fictional third country.

Diplomatic efforts to resolve the crisis over Iran's nuclear activities need to be pursued with "urgency," the head of the U.N. atomic agency said Thursday.

"The IAEA is firmly committed to dialogue," International Atomic Energy Agency head Yukiya Amano said at the start of a two-day meeting of the U.N. body's board set to be dominated by Iran's program.

Pakistani warlord Mullah Nazir, who sends men into Afghanistan to fight US soldiers, was wounded Thursday in a suicide attack that killed two other people, security officials said.

Nazir is the main warlord affiliated to the Pakistani Taliban in South Waziristan, one of seven districts that make up the semi-autonomous tribal belt considered a base for al-Qaida and other Islamist militants.

The United States reaffirmed on Wednesday that it intends to vote against a Palestinian request for enhanced status at the United Nations.

"We intend to vote no.... We think this is a mistake," State Department spokeswoman Victoria Nuland said. "We oppose this move altogether."