Obama greets police officers at the First Precinct police station  in New York US President Barack Obama paid solemn tribute at the site of the downed Twin Towers, days after 9/11 architect Osama bin Laden was shot dead by American commandos in his Pakistani lair. Intel found in bin Laden\'s compound revealed Al-Qaeda was considering a possible train attack at an unspecified location in the United States to grimly mark this year\'s 10th anniversary of the September 11 attacks.
US officials played down any imminent threat, describing the plot as \"aspirational,\" but it did perhaps indicate that bin Laden remained more integral to the everyday running of Al-Qaeda than previously thought.
In a moment of high symbolism in New York, Obama laid a wreath at Ground Zero before hugging relatives of those killed when Al-Qaeda extremists, presumed to be acting on bin Laden\'s orders, plowed their hijacked planes into the World Trade Center and the Pentagon.
Despite the momentous nature of the Al-Qaeda leader\'s death, almost a decade after his attacks drove a wedge between the West and the Muslim world, the ceremony was low-key and somber: a remembrance of those nearly 3,000 fallen rather than a victory celebration.
Obama, making his first visit to Ground Zero as president, did not make a speech, but solemnly bowed his head and observed a moment of silence after laying the wreath along with city officials.
He spoke briefly earlier at a firehouse that lost 15 men battling the infernos on 9/11, issuing a stark message to America\'s enemies around the world. \"When we say we will never forget, we mean what we say,\" he said.
Obama is to visit Fort Campbell in Kentucky on Friday to meet some of the elite commandos who sneaked into Pakistan in stealth helicopters and took out bin Laden in the death of night.
The president \"will have the opportunity to privately thank some of the special operators involved in the operation,\" a US official said on condition of anonymity.
The commandos who swooped on Osama bin Laden\'s compound in Abbottabad on Monday reportedly came from a renowned squad known as \"Team Six,\" an elite unit drawn from the already elite ranks of the SEALs.
The fallout from the covert pre-dawn raid meanwhile intensified with Pakistan\'s military demanding the United States cut its troop presence in the country to a \"minimum.\"

After days of questions in Washington over how bin Laden could have found shelter under military noses, Pakistan\'s army chief of staff General Ashfaq Kayani threatened to \"review\" cooperation in the event of another US raid.
A key US ally in the war against Islamist militants in Afghanistan, Pakistan has admitted \"shortcomings\" in developing intelligence on bin Laden\'s whereabouts and ordered an investigation.
But Islamabad is fighting hard to allay suspicions that bin Laden could have had some kind of support from its military intelligence services.
\"It\'s easy to say that the Inter-Services Intelligence (ISI) or elements within the government were in cahoots with the Al-Qaeda,\" top foreign ministry official Salman Bashir said.
\"This is a false hypothesis. This is a false charge. It cannot be validated on any account and it flies in the face of what Pakistanis and in particular the Inter-Services Intelligence has been able to accomplish.\"
In Washington and beyond there is incredulity that bin Laden could have found shelter for up to six years in Abbottabad, a leafy garrison town just two hours\' drive from the capital.
In a sign of complete US distrust of its key ally, CIA chief Leon Panetta has said Washington kept Islamabad in the dark about the raid for fear of the Al-Qaeda chief being tipped off.
Despite some US lawmakers questioning billions of dollars in US assistance and accusing Pakistan of playing a double-game, key leaders in Congress voiced support Thursday for preserving aid.
\"It\'s not a time to back away from Pakistan: It\'s time for more engagement with them, not less,\" House Speaker John Boehner told reporters.

The United States has given some $18 billion to Pakistan since the September 11, 2001 attacks, when the nuclear-armed nation officially ended support of Afghanistan\'s Taliban and agreed to work with the United States.
While quietly rejoicing at the elimination of America\'s most wanted man, the Obama administration has been forced to defend the legality of the raid, after acknowledging that bin Laden was unarmed when he was shot fatally above the left eye.
The US Navy SEALs who raided bin Laden\'s compound found an AK-47 and a pistol in his room, a US official told AFP Thursday, offering more details about the operation.
\"He had weapons in his room, more than one,\" said the official, who spoke on condition of anonymity. \"He was not compliant. He did not surrender.\"
Divulging more details of the raid after conflicting accounts from the White House, the official said the US commandos encountered only one man who was armed at the compound -- bin Laden\'s courier -- who fired the only shots near the start of the nearly 40-minute operation.
The courier \"was the only one who opened fire,\" he said.
US media reported that the courier was killed along with his wife in a guesthouse adjacent to the main residence where bin Laden was hiding.
At the larger three-storey building, the Americans shot and killed the courier\'s brother, who reportedly had one hand behind his back.
Making their way up the stairs, they saw bin Laden\'s son, who \"lunged\" towards them, the New York Times reported.
On the third floor, bin Laden was shot in the chest and head.
The official insisted the US team faced an array of potential dangers by venturing into the hideout of Al-Qaeda\'s mastermind, and were prepared for the possibility he and his comrades might be wearing suicide vests or have explosives planted ready to be triggered
\"It\'s important to see the context,\" he said.
\"If you are going to a house where the people have been hostile, it\'s Osama bin Laden\'s house, and you see him in a room and he\'s not compliant -- what would you do?\"
Obama, on Wednesday, opted against releasing photos of bin Laden\'s corpse, citing national security risks and saying the United States should not brandish \"trophies\" of its victory.
Bin Laden\'s body was buried at sea off a US warship to prevent any grave on land from becoming a shrine. The Abbottabad compound that served as his lair instead risks becoming a macabre monument to the Al-Qaeda leader.