WASHINGTON: A Trump administration official has urged countries not to buy military hardware from Russia and China , asserting that America's competitors were using arms sales as key tools to build their own influence around the world.Although the official did not name any country, Washington has in the past cautioned India that its decision to buy the long-range S-400 Triumf missile defence system from Russia will have serious implications on defence ties.India and Russia signed a USD 5 billion S-400 air defence system deal in October last after wide-ranging talks between Prime Minister Narendra Modi and Russian President Vladimir Putin.In a major policy speech, Assistant Secretary of State for Political Military Affairs Clarke Cooper on Thursday said that a partnership with America offers something a purchase from Russia or China never will: friendship."Our competitors are turning to arms sales and security assistance as key tools to build their own influence around the world, and to weaken ours," he said.In his speech on 'America As The Partner of Choice' at Meridian International Center , the top American diplomat illustrated with multiple, specific examples that those who seek to purchase Russian and Chinese military equipment should consider carefully and follow the rule of Caveat emptor -- a principle that the buyer alone is responsible for checking the quality and suitability of goods before a purchase is made.In contrast, the United States offers quality, transparency and accountability, and a long term, secure, and sincere partnership in support of shared security interests and common values, he said.Cooper identified China and Russia as strategic competitors whose efforts have been to proliferate arms around the world."We have come a long way since the AK-47 became the ubiquitous symbol of Soviet-backed insurgencies from Southeast Asia to Africa. Today, Russia is working hard to foist variants of its S-400 air defence system around the world, while China is supplying everything from armoured personnel carriers to armed drones."To quote another Latin phrase - caveat emptor! - Buyer, beware. We have seen countries around the world leap at the chance to obtain high-tech, low cost defensive capabilities only to see their significant investments crumble and rust in their hands," Cooper said."It is true that the United States remains far and away the greatest provider both of direct security through the deterrence of our alliances and the presence of our global forces, true we remain the single greatest provider of grant security assistance, to the tune of over USD 10 billion a year between State and Defence, and, true we remain far and away the most significant source of defensive equipment for countries around the world," he said.Cooper alleged that through the targeted marketing of systems like the S-400, Russia seeks to exploit the genuine security requirements of partners to create challenges in US' ability - legal and technological - to provide them with the most advanced defensive capabilities.And through a combination of cut-price systems such as unmanned aerial systems, predatory financing mechanisms and sometimes outright bribery, China is using arms transfers as a means of getting its foot in the door - a door that, once opened, China quickly exploits both to exert influence and to gather intelligence, he said."It is true, if we scratch the surface of the offers laid out by our adversaries we find failed systems, flawed training, false bargains. And it is important countries around the world understand the risks of choosing to procure systems from China or from Russia."But while it is important that we lift the veil on our strategic competitors, it is more important that we make the case for why partnering with America is not just the better choice, but indeed the best choice," Cooper said.It is the quality of US defence equipment. It is American commitment not just to make deals, but to build capabilities, he said."It is the transparency, accountability, and predictability of our policies and processes. And it is the reassurance that comes from partnering with the United States military," Cooper asserted.The United States is the preeminent global security partner in both the capabilities it provides, and the reassurance that comes with its friendship.US defence equipment remains far-and-away the most capable in every warfighting domain, from the F-35 to the Theater High Altitude Air Defense (THAAD), from its electronic warfare suites to early warning radars, from the Apache in the air to the Joint Light Tactical Vehicle on the ground to the Multi-Mission Surface Combatant in the oceans, he added.The S-400 is known as Russia's most advanced long-range surface-to-air missile defence system. China was the first foreign buyer to seal a government-to-government deal with Russia in 2014 to procure the lethal missile system.