India's greatest architectural marvel is threatened with possible monsoon flood damage because of work on a nearby riverbank where a $40 million restaurant and shopping complex was planned.

The government has halted construction, but experts say that what has already been done has hemmed in the Jamuna River, and it could rise and flood the gardens of the Taj Mahal, just 300 metres away.

Particles in the water may harm the monument's white marble, and stones could pound its foundation.

"Sand filling and piles of red sandstone on the riverbed of the Jamuna would damage the basic structure of the Taj when the water level goes up in the monsoon," said DK Joshi, of the monitoring committee appointed by India's Supreme Court.

The Taj Mahal was built by the Mogul Emperor Shah Jahan in the 17th century as the tomb of his favourite wife, Mumtaz Mahal. Its spires, walls and dome took 22 years to build and it was completed in about 1647. - Sapa-AP