IT'S EXCEEDINGLY RISKY for an American President to get involved in the religious wars of Northern Ireland, but at least Mr. Carter seems to see the danger. His statement, issued on Tuesday after weeks of rumor and speculation, is a model of caution. The trouble is that not all of the people reading it are going to be as cautious as he is. He will have to guard against the inevitable attempts to draw him into a mediator's role and to make him weaken the one essential condition for his aid.

The justification for this initiative is that the guerrilla warfare in Northern Ireland is now in its eighth year, with no end in sight. A lot of Americans worry about it -particularly those whose families came here from Ireland. The administration can argue with some justice that there will always be a lot of American interest and involvement in Irish affairs, and Mr. Carter's statement is only an attempt to preempt the wrong kind with the right kind.

The wrong kind is, of course, the flow of contributions to buy arms for the Irish Republican Army. That flow has dropped sharply over the past year or two, as Americans have come to realize that the money goes to a terrorist organization whose victims have predominantly been not British soldiers, but Irish civilians, including small children. A strong appeal to cut off the money for the gunmen was launched last St. Patrick's Day by House Speaker Thomas O'Neill, Sens. Edward M. Kennedy and Daniel Patrick Moynihan, and Gov. Hugh Carey of New York. It was a statesmanlike gesture, but it was followed by a ripple of anxiety among other Irish-Americans that it addressed only the Catholic side of this covert war. The Protestants of Northern Ireland are, after all, the majority, and their irregular military organizations are at least as heavily armed, and as quick to violence, as the IRA.

In June the four politicians met with Secretary of State Cyrus Vance to ask what further might be done. The State Department talked at length with Britain, to which Northern Ireland belongs, and the Irish Republic, which it adjoins. The result was the President's statement promising aid - but only if there is peace.

Peace requires a political settlement between the Protestant majority and the Catholic minority, with the minority getting a genuine share of power. The Northern Irish are going to have to work that out among themselves, the President said. But if they can do it, the United States will "see how additional jobcreating investment could be encouraged," a powerful inducement in a province where the unemployment rate is now double Britain's average.

Sen. Kennedy immediately added a suggestion that this aid could take on the dimensions of a small Marshall Plan with grants, loans "and other incentives and subsidies for U.S. firms to invest in Northern Ireland." The senator may well be pushing the administration a bit further than it cares to go just yet. But, having gotten into this affair, Mr. Carter ought not to be excessively vague about the nature of the promise he is making. It is worth something to Americans to see peace in that battered province, and the United States is now putting up a cash prize for the peacemakers.