Remember the potentially important breakthrough toward peace in the Middle East that was made last month? Remember how PLO leader Yasser Arafat promised to renounce terrorism and recognize Israel's right to exist?

That promise prompted the United States to reverse a 13-year policy and start talking with the Palestinian Liberation Organization.But how sincere was Arafat in making that pledge? There's room for reviewing the new U.S. stance based on the Arafat pledge.

A review is clearly in order in light of recent evidence that Arafat may have strayed from his commitment to renounce terrorism. If he won't keep that promise, how far can he be trusted to make good on his vow to recognize Israel's right to exist?

The disturbing new evidence consists of the purported statement by Arafat that the PLO would "pump 10 bullets into the chest" of anyone trying to stifle the Palestinian uprising on the Israeli-held West Bank and in Gaza.

Though Arafat denies having made that statement, the U.S. State Department claims to have a tape recording of it. And if Arafat is threatening people who happen to be moderates, he is threatening whatever prospect of peace there may be in the Middle East.

In all fairness, the U.S. needs to watch not only what Arafat says but also what he does. On this score, there's some room for encouragement. Even the Israeli army reports that Arafat's wing of the highly-splintered PLO has neither planned nor carried out guerrilla actions in the past two months.

Consequently, Washington doesn't need to reverse itself and stop talking to the PLO again - at least not yet. Even so, Arafat clearly needs to watch what he says. The PLO leader can't be taken seriously in Washington if his rash statements put his credibility constantly in doubt.