The State Department, reacting to reports that Israel is seizing for new settlements in the occupied West Bank, yesterday called such acts "unhelpful to the peace process [in the Mideast] and ill-advised."

In a partial return to the language used by former president Carter's administration, a department statement said: "Such unilateral acts tend to pre-judge an issue which must be addressed through negotiations."

It added that President Reagan and Secretary of State Alexander M. Haig Jr. "have indicated that the continued creation of settlements can only harm the prospects for negotiations" on determining the future of the Palestinian-populated West Bank, which Israel has occupied since 1967.

But, while the statement clearly was meant as a signal of deep U.S. displeasure at the Israeli actions, it stopped short of calling them "illegal," as had been the policy during the Carter administration.

The question of whether the U.S. government now considers Israeli settlements in occupied territories "illegal" has been a question of some delicacy in the State Department since last week, when Reagan, in a newspaper interview, said he disagreed with the previous administration's interpretation.

In the interview, Reagan said, "As to the West Bank, I believe the settlements there -- I disagreed when the previous administration referred to them as illegal; they're not illegal. Not under the U.N. resolution that leaves the West Bank open to all to-all people -- Arab and Israeli alike, Christian alike."

That caused several Arab countries to ask for clarification of the U.S. position. However, the State Department subsequently denied that Haig or any of his key aides were in disagreement with the president's comments.

In the interview, Reagan did say he thought establishment of Israeli settlements at this time was "ill-advised" and "unnecessarily provocative.

The statement issued yesterday appeared to be an attempt to bring the department's position into line with that view -- namely, with the settlements it does not regard them as necessarily illegal.