Ariel Sharon’s threat to assassinate Yasser Arafat should be taken very seriously. The Israeli prime minister has killed before and may very easily kill again. He has got away with murder before; he has killed hundreds, maybe thousands of Palestinians. Most recently, in less than a month, he assassinated the founder of Hamas then the man who replaced him. Those two killings passed without Palestinian reprisals — at least so far — and without so much as a slap on the wrist from the United States. As a result, Sharon believes, perhaps correctly, that he can get away with murder again.

The Bush administration says it staunchly opposes the assassination of the Palestinian leader considering “a pledge a pledge” even after Sharon told Israeli television that he no longer considered himself bound by a promise made to President Bush not to harm Arafat. But Sharon has already taken what he wanted from the United States. He could not have asked for more than Bush promised him: Keeping large parts of the West Bank, ruling out the possibility of Israel returning to the pre-1967 borders and denying the right of return to Palestinians.

The Sharon-Bush project would reduce the West Bank to three or four disconnected and badly truncated Bantustans, effectively thwarting hopes of a future Palestinian state including the Gaza Strip and the entire West Bank. These are unprecedented concessions by an American administration and one that no new administration in the future will be able to ignore or abrogate. Thus, after extracting what no Israeli leader has ever been able to from any American president, Sharon is undoubtedly on a roll and naturally assumes he can do anything, including literally getting away with murder. There are no more red lines; nothing is off limits. What better example than the killing of the Hamas leader Abdelaziz Al-Rantissi? The first thing Sharon did after leaving Washington was to order Rantissi’s assassination. Washington’s reply, in not so many words: Sharon did the right thing.

For the most part, White House officials attribute Sharon’s assassination threat against Arafat to the challenge he faces in selling his plan to withdraw from Gaza and remove settlements to hard-line members of his own Likud Party and to the Israeli people. Likud’s 200,000 members will vote on May 2 on the pullout. The latest opinion polls show that supporters of Sharon’s initiative have sharply fallen even though they remain the majority. So perhaps Sharon’s tough talk is politically calculated to mollify hard-liners within the Likud Party ahead of the internal vote. The threat, however, cannot be taken for granted. In recent months, while Israel repeatedly threatened Arafat, it took no action save to decide in September that he should be “removed,” an intentionally vague statement. Sharon is much clearer in his intentions. There can now be no mistake. Arafat is a marked man.