The call came as Riyadh was in the process of concluding negotiations with the US and other nations on entering the WTO.

Twelve members of the House of Representatives and five senators made the demands in two separate letters to US Trade Representative Robert Zoellick.

'These negotiations have failed to fully address Saudi Arabia's participation in and support for the Arab League boycott of Israel. This is unacceptable,' the letter said. It also noted that US law instructs the US Trade Representative to 'vigorously oppose' WTO membership for any country that 'fosters, imposes, complies with, furthers, or supports' a boycott such as the Arab League's on Israel.

A spokesman for Zoellick said the Bush administration was 'mindful of the various requirements set by Congress and we have and will continue to consult with them on this very sensitive and important issue.'

According to Zoellick's office, Riyadh continues to enforce the 'primary level' of the Arab League boycott, which means it bans foreign companies that have imported Israeli products from exporting to Saudi Arabia.

While acknowledging Saudi steps to dissolve a Riyadh-based charity suspected of funding Al-Qaeda, the senators' letter said they remained 'concerned about the depth of the Kingdom's support for the US-led war on terror.'