Most Americans approve of the way President Clinton is handling his job, but a majority also believe he lied under oath about whether he had sex with Monica Lewinsky, according to one new poll.

Three surveys taken since last weekend come amid rapid-fire developments in special prosecutor Kenneth Starr's investigation of whether President Clinton had an affair with Lewinsky and then tried to cover it up.In a CNN/USA Today/Gallup Poll taken Wednesday, Clinton's approval rating was 65 percent. That was almost the same as in an NBC News/Wall Street Journal Poll taken from last Saturday through Monday.

But two thirds of those questioned in the CNN/-USA Today/-Gallup Poll thought it was definitely or probably true that Clinton had sexual relations of some kind with Lewinsky. And 56 percent believed he definitely or probably lied under oath about it.

While 43 percent thought the president definitely or probably tried to obstruct justice, only 24 percent of all those responding thought obstruction was a serious enough matter for Congress to consider impeachment while 41 percent thought obstruction was serious, but not grounds for impeachment.

The same number, 63 percent, thought both the president and Lewinsky were very likely or somewhat likely to tell the truth. But 31 percent of the respondents thought the president was very likely to tell the truth, while only 23 percent thought it very likely Lewinsky would be truthful.

The Gallup telephone survey of 622 adults had a margin of error of plus or minus 4 percentage points.

A CBS News poll released Wednesday found that most Americans think the president should testify before the grand jury, but they disapproved of the immunity deal Starr offered for Lewinsky's testimony. The CBS poll found that 60 percent thought Clinton should testify while 37 percent thought he should not.