"We are close to finalising our agreement on tariffs with Saudi Arabia, and we are increasingly more comfortable that the multilateral issues will be addressed satisfactorily," acting US Trade Representative Peter Allgeier said in a letter on Friday to Senator Blanche Lincoln, an Arkansas Democrat.
US President George Bush will host Saudi Crown Prince Abd Allah at his ranch in Crawford, Texas, on Monday.
In the lead-up to that meeting, US and Saudi trade negotiators have been working around the clock to finalise a bilateral deal on the terms ahead of Riyadh's entry into the WTO, an industry official said.
"I think they would like to be able to make an announcement in Crawford. But whether or not they are going to narrow the final gap by then is really up in the air," the industry official said.
One potential snag is a human rights issue that Lincoln raised on Thursday at a Senate Finance Committee hearing on the nomination of Representative Rob Portman, an Ohio Republican, to be the next US trade representative.
She urged the United States not to sign off on a deal allowing Saudi Arabia into the WTO until the country has made
"meaningful progress" towards resolving a child abduction case dating back to 1997.