Nine international companies have expressed interest in providing design and consulting services worth OMR60m ($155m) for the first major rail project in Oman.
Bids had initially been asked to be submitted in July 2012, but the deadline has been extended to 5 October 2012 to allow enough time for new offers to come in.
According to reports, interested bidders include a consortium of Denmark's COWI and DBI and Aecom of the US, Systra of France, US-based Parsons, and Mott MacDonald of Britain.
Other bidders who have shown interest include a consortium of Italy's Italferr and Worsely Parsons of Australia, an unnamed China-based railway company, France's Egis Rail, Pointec Group, and a consortium of Korea Rail and Hyundai Group.
Oman plans to build a 1,000km railway at an estimated cost of OMR5bn ($12.9bn), which is expected to be completed in 2018.
The new line is part of a plan to build rail links across Gulf Cooperation Council (GCC) countries.
New terminals will be built at major towns along the way to transport goods and passengers as the railway will run from the northern border town of Buraimi to the southern city of Salalah.
Each country in the GCC, which includes Oman, Saudi Arabia, the United Arab Emirates, Kuwait, Qatar and Bahrain, is planning to build their own railway system as part of a pan-Gulf rail system to increase trade among member states.