Singapore shares opened muted in negative territory on Tuesday after a long weekend, as uncertainty around the Middle East crisis resolution dampened investor sentiment.

The Straits Times Index opened 0.06%, or 3.25 points lower, at 5,695.180.

While Iran is reported to be close to a deal with Oman to reopen the Strait of Hormuz, it continues to hold a hard stance on direct negotiations with the US until its conditions are met.

Investors will also be keenly watching Wednesday's U.S. consumer price index data for cues on the Federal Reserve's next move on interest rates.