"IT'S the exact opposite of patriotism and heroism to walk out and shoot two law-enforcement officers in the back", the President's spokesman said.
While the President's reaction to the killing of the two RUC officers in Lurgan at a time when hopes for a reinvigorated peace process were high was his harshest yet, he did not go as far as Senator Edward Kennedy, who said: "Now is the moment of truth for Sinn Fein."
Senator Kennedy added: "They must produce a ceasefire or else join in condemning the violence and dissociate themselves completely from all those who continue to commit or condone those wanton acts of terrorism."
President Clinton's spokesman, Mr Mike McCurry, was deliberately vague, however, when asked directly: "What does today's development do to the President extending a hand to Gerry Adams? What will the administration's attitude be henceforth with regard to Adams and Sinn Fein?"
Mr McCurry referred to a reply to an earlier question, when he was asked: "Do you believe that the US will continue to have discussions with Sinn Fein even if these atrocious acts keep happening?"
His reply to that had been: "The United States government has had contacts with parties that we have always believed have been helpful to the process. But, sooner or later, it becomes clear who is willing to help the process and who is not."
Pressed to explain what he meant by this, Mr McCurry refused to do so, but added: "I think we're at a point now where actions are going to demonstrate a lot, because there have been some actions that, frankly, have demonstrated things that are outrageous and heinous. What we need to see now is a restoration of the ceasefire, an unequivocal restitution of a ceasefire that lasts by the IRA."
A persistent US reporter asked if Mr McCurry's statement that "sooner or later it becomes clear who's willing to help the peace process and who's not" could be interpreted as "a thinly-veiled hint that patience with Sinn Fein could run out". Mr McCurry again refused to elaborate.
An administration official later said that President Clinton had been expressing his abhorrence at the IRA murders rather than addressing the question of continuing White House contacts with Sinn Fein. However, the killings have yet again raised doubts in Washington about the influence of Mr Adams on the IRA.
The US administration has been hearing for some time now from Sinn Fein that there would be an IRA ceasefire if the conditions were right. Whatever the relationship between Mr Adams and the IRA, it was "impossible to believe that this (the killings) helps him in any way towards getting a ceasefire", the official added.
If it becomes clear "sooner or later" that Sinn Fein is not willing to help the peace process, Washington could decide that it is time to cut the line of communication.