LEARNING that the United States Government has once again lied to its people, or that the Executive branch has lied to Congress, provokes a mixed reaction. One is grateful - even proud - to be living in a society in which such lies can be exposed in bold type across the front page. But the news itself, and its dreadful familiarity, remain sickening. This time round, the news in question comes via El Salvador, a tiny Central American country of around five million people. Last month a special United Nations investigative body, the Commission on Truth, released its report on atrocities and murders committed during El Salvador's decade-long civil war, which formally ended last year. The report confirms what the Carter, Reagan and Bush administrations consistently denied that the vast majority of the approximately 75,000 civilians murdered during the war - many, if not most, women and children - were killed by US-backed military and para-military death squads. That finding certainly does not vindicate the five to 10 per cent of the killings carried out by opposing rebels. But at least the rebels were not trained, funded and directed by the US Government. If the mass murder and torture committed by the El Salvador Government and its terrorists over the course of 12 years had somehow escaped the notice of American officials, we could take comfort in the knowledge that US foreign policy was simply misguidedand grossly inept. The truth about El Salvador, however, is far uglier than that. The rationale for deep US involvement in a dirty little civil war in Central America was the same one that has launched many an American ship: stopping the spread of communism. The US, proclaimed then-Secretary of State Al Haig, would ''draw a line in ElSalvador''. And draw it we did, with blood money. From 1980 through 1992, the US pumped US$6 billion (HK$47 billion) into El Salvador - US$1,500 for every man, woman and child in the country. (The rebels had some backing from Cuba and Nicaragua, but nothing on the same scale.) The problem with this largely military assistance is not just that it failed (unless a draw can be considered a victory), but that it was extended in wilful violation of US law. Because of reports by human rights groups and journalists of right-wing atrocities, Congress mandated that continuing assistance to the El Salvador Government depended on White House certification of substantial ''progress'' in curtailing such abuses. So determined was the Reagan administration to keep the money flowing, however, that it chose to ignore damning evidence that might have blocked US assistance. When the US ambassador attributed the assassination in 1980 of Archbishop Oscar Romero to El Salvador's top right-wing politician, Washington ignored his dispatches. When four American church women were murdered, then-US Ambassador to the UN, Jeane Kirkpatrick, strongly implied they had it coming because they were involved in politics. Mr Haig helpfully suggested that the women might have been shot after running a roadblock, though all of them died from a close-range bullet in the brain. In 1981, when the New York Times and Washington Post journalists reported the massacre of 200 peasants in the village of El Mozote by a special, US-trained elite force, the Reagan damage-control team went into high gear. Even after their own investigators confirmed the newspaper accounts, the State Department insisted that there was ''no evidence'' of a massacre, and suggested that the two journalists who had reported it were communist dupes. The killings continued, day-by-day, year-by-year, until two per cent of El Salvador's population had been dispatched to an early and, in all likelihood, shallow grave. In 1989, six priests, including the rector of San Salvador University, were executed under cover of darkness, and once again the US Government had a good idea who ordered the killings. But rather than expose its protege General Rene Emilio Ponce, the Bush administration engineered his promotion to defence minister. The UN report also points the finger at Mr Ponce, who resigned his post the day before the report came out. Does it all matter? Should we give a damn if well-motivated (if misguided) US officials say one thing and do another? Does the secret sale of weapons to Iran, illegal transfer of technology to Iraq, complicity in the cover of an international banking scandal - does any of it matter? Of course it does, because the bedrock of American society is a government that is accountable to its people. Americans are far more forgiving of government deception in foreign affairs than at home, but the principle is exactly the same in either case. When senior US officials, up to and including the President, circumvent the law, they subvert the integrity ofthe political system they have sworn to protect. And when their deception is discovered, the cynicism it breeds further corrodes that system. ''Revealing the truth has to be a key element of an act of national reconciliation,'' noted the current State Department spokesman in response to the UN report. He was presumably referring to El Salvador, where reservoirs of bad blood accumulated during 12 years of brutal and vengeful fighting could still spill over. But the spokesman might just as well have been talking about the United States, and the need for reconciliation between a government that habitually lies, and a people who feel insulted because they are asked to swallow those lies.