The JCI fell by as much as 5 percent in the first trading session on Wednesday, while the rupiah weakened to Rp17,930 per U.S. dollar.

Analysts said the rupiah may weaken further as Iran halts talks with the U.S. and threatens to close the Strait of Hormuz.

The stability of the rupiah exchange rate will be a crucial factor in determining the direction of JCI for the week.