Most Southeast Asian markets ended higher on Tuesday, as investors took a cautiously optimistic stance ahead of a U.S. Federal Reserve policy meeting that could provide cues on the pace of rate hikes in the months to come.

A poll of 100 economists conducted last week showed the Fed was certain to push interest rates up by 25 basis points to 1.00 percent-1.25 percent at its June 13-14 meeting.

However, the conviction for a move beyond a widely expected rise this month has faded for many forecasters along with the outlook for inflation for most.

"(We) expect Asian bourses to continue to tread water with a topping of caution ahead of the Federal Open Market Committee (FOMC)," OCBC Bank said in a note.

The positive sentiment across the region was also supported by oil prices, which edged up following statements that OPEC leader Saudi Arabia was making significant supply cuts to customers.

Vietnam extended gains to post its highest close in over nine years, underpinned by financial and industrial stocks.

Gains on the benchmark index were broad-based with eight of nine sectors in positive territory.

Singapore shares shed the previous day's losses, boosted by gains in the city-state's "big three" banks.

The final first-quarter jobless rate was revised down from the preliminary estimate of 2.3 percent.

Indonesia edged higher, led by gains in consumer staples.

Indonesia's central bank is expected to keep its benchmark interest rate unchanged on Thursday, just hours after the Fed decides on interest rates, a Reuters poll showed.

Philippine shares closed lower with real-estate stocks accounting for nearly half of the losses.

The country has been seeing a violent conflict in the southern town of Marawai, where a siege by fighters allied to Islamic State, has stoked concerns of instability among Southeast Asian nations.