SINGAPORE shares ended a tad firmer, but upside was capped by analysts' warnings that the high market valuations inspired by the technology rally in the US may lead to profit-taking.

Investors were mostly sidelined ahead of the US Fed's publication of its Beige Book report on the state of the economic health of the nation on Wednesday.

"We ask ourselves the same question over and over - how extended are valuations?" David Kotok, chief investment officer at Cumberland Advisors Inc, said on Bloomberg TV. "Then we see reports on earnings and there are positive earnings surprises coming from the tech companies and that would suggest if that momentum continues then in fact they are not yet overvalued."