The U.S. ambassador said Washington could understand the Israeli response.
The violence could have an impact when Sharon battles on Sunday to hold on to the leadership of his ruling Likud party in a showdown triggered by rightist rival Benjamin Netanyahu's opposition to the Gaza pullout.
Netanyahu said it would bring more violence rather than the "disengagement" from conflict Sharon said he sought.
The vote by more than 3,000 central committee members on Monday could prompt Sharon to leave Likud and form a new centrist alliance if it brings forward party primaries as Netanyahu wants.
The violence also poses a challenge to Abbas, who has shied from disarming militants for fear of causing civil war. Because of the trouble in Gaza, Palestinian lawmakers postponed a vote of no-confidence in Prime Minister Ahmed Qurie's government, called over a worsening internal security situation.