WASHINGTON (Reuters) - The United States has fretted for years that its ties to Pakistan and past sanctions against India would harm its efforts to win arms deals such as the $11 billion fighter order that slipped away from two US suppliers this week, a US diplomatic cable showed. "Our ability to seize the opportunities presented by this newly improved environment is limited by the commonly held view that the US will not prove to be a reliable supplier of defence equipment," Timothy Roemer, the US ambassador to India, said in an October 29, 2009, cable to Michele Flournoy, a top Pentagon official then about to visit India. US officials from President Barack Obama down subsequently pushed hard to sell US fighter jets to India to crown expanding security ties. The United States also is eyeing tens of billions of dollars in other potential arms deals with India, the cable showed. In the end, India shortlisted two European aircraft over Boeing Co's F/A-18 SuperHornet and Lockheed Martin Corp's F-16, company officials said on Thursday. Lockheed and Boeing are the Pentagon's No. 1 and No. 2 supplier, respectively. Each is pressing to boost sales in India, which plans to spend about $50 billion in the next five years to modernize old Soviet-era weapons and technology. Roemer announced Thursday he was leaving his post for professional and family reasons. "The new environment" reference in his 2009 cable concerned the emergence of Prime Minister Manmohan Singh's government with "a clear mandate not beholden to coalition partners" for the first time since post-Cold War US-Indian strategic ties took shape. US competitors use the economic sanctions imposed by Washington after Indian nuclear tests in 1998 to try to harm US sales prospects, the cable said. They also point to "our close defence relationship with Pakistan as rationale that the US should not be trusted," Roemer wrote in the message obtained by the anti-secrecy group WikiLeaks and made available to Reuters by a third party. The cable cited one unnamed source as saying the Indian army will never put US equipment in divisions facing Pakistan, India's historic foe, "because they expect the US will stop military supplies in the event of Indo-Pak hostilities." The US Defence Department said on Friday it was "deeply disappointed" by rejection of the US bid to supply 126 new fighter aircraft. Instead, India set up a contest between France's Rafale and the Eurofighter Typhoon made by Britain, Germany, Italy and Spain. "We look forward to continuing to grow and develop our defence partnership with India," said Navy Commander Leslie Hull-Ryde, a Pentagon spokeswoman, "and remain convinced that the United States offers our defence partners around the globe the world's most advanced and reliable technology." She said US officials were closely studying Indian-provided documentation on the short-listing decision, and looked forward to a full "debrief" from the Indian Air Force. A State Department spokeswoman, Heide Fulton, declined to comment on Roemer's 2009 cable as a matter of policy. A senior State Department official said the United States was not aware of any allegations of impropriety "so far" in the fighter matter. The full field included the two American planes, three Europeans and a Russian model. Asked about the possible impact of any Indian concerns over US reliability as a supplier, the official said the elimination of Boeing and Lockheed seemed to be based on technical considerations. "I think, if anything, the concerns are that it was only made on that basis and without looking at the wider strategic implications of this," the official said. In the past three years, India has agreed to buy some $10 billion in US military hardware including six Lockheed C-130J military transport planes and eight long-range Boeing P-8 maritime reconnaissance and anti-submarine warfare aircraft.