Speaking to reporters on his plane before his arrival in New Delhi on Tuesday, Gates expressed admiration for how Indian leaders reacted to the 2008 attacks that left 166 dead.
"The bombing in Mumbai was a really terrible event and frankly I believe that the Indians responded subsequently with a great deal of restraint and have conducted themselves in a very statesmanlike manner since that attack."
India has blamed the assault by 10 heavily-armed gunmen on the Pakistan-based Islamist group Lashkar-e-Taiba, and called for stepped up pressure on Pakistan to rein in militants.
"I think that even within the framework of that attack and the suspicions that it created that the two sides have managed to keep the tensions between them at a manageable level," Gates said.
His comments came before a visit to India in which the threat posed by militants in Afghanistan and Pakistan will be high on the agenda.
Gates, who was due to meet Prime Minister Manmohan Singh, Foreign Minister S.M. Krishna and Defense Minister A.K. Antony, said that India and the United States faced a common threat from violent extremists.
"Both of our countries know all too well the terrible human cost of terrorist attacks," Gates wrote in a commentary in The Times of India before his arrival.
Leaders of both governments have agreed to expand cooperation in sharing tactics and information in countering terror threats, including efforts to disrupt militant financial networks and safeguard public transit, he wrote.
In his talks with Indian leaders, Gates told reporters he also planned to provide an update on the NATO-led war in Afghanistan, a mission that India has strongly endorsed.
Washington has been grateful for India's generous reconstruction aid to Afghanistan and steadfast backing for the war against Taliban insurgents.
After decades of mutual unease during the Cold War, India's relations with the United States have steadily improved and defense ties have expanded since the attacks of September 11, 2001, including annual joint military exercises.
Defense-related trade is also on the rise after a deal in July between the two countries opened the way for the sale of sophisticated US weaponry to India.
Gates called the "end-use monitoring" agreement "hugely important" but said more needed to be done to expand arms trade between the two countries.
He said more US legal barriers needed to be removed that would give India access to American-made military hardware, citing agreements on communications and logistics cooperation that still needed to be sealed.
In his newspaper commentary, Gates wrote that "we both have to reexamine policies dealing with exchanging technology" and US regulations particularly needed to be reformed.
India last year bought six Hercules transport aircraft from US aviation giant Lockheed Martin and Boeing said this month that India had expressed interest in a potential purchase of 10 C-17 transport planes.
The US defense firms also are keenly interested in a lucrative contract to build fighter jets for India, along with European, Russian, French and Swedish companies.
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