NEW YORK (CNN/Money) - In a move that could hurt relations between the United States and Saudi Arabia, the oil- and gas-rich country is refusing to open its most promising natural gas fields to outside companies, according to a published report Monday.

The Wall Street Journal, quoting unidentified executives with major oil companies that had been in discussions with the Saudis, said that the country's foreign minister outlined the new position in a letter to the companies last week. Among the companies that had been in negotiations on possibly investing $25 billion in new facilities in Saudi Arabia were Exxon Mobil Corp. (XOM: Research, Estimates), Royal Dutch/Shell Group (RD: Research, Estimates), BP PLC (BP: Research, Estimates), France's TotalFinaElf SA (TOT: Research, Estimates), Marathon Oil Corp. (MRO: Research, Estimates), Occidental Petroleum Corp. (OXY: Research, Estimates), and the newly merged ConocoPhillips (COP: Research, Estimates).

A spokeswoman for ExxonMobil told CNNfn she could only confirm that the companies have received a response from the Saudis to their investment proposal. A spokesman for Royal Dutch/Shell was also limited in his comments.

"We are now evaluating these latest proposals and expect to refer back to the (Saudi)government before the end of the month," said Royal Dutch/Shell spokesman Jason Everard. BP had no comment when contacted by CNNfn.

Saudi Arabia has produced all of its own oil and gas since the 1970s. The discussions about allowing the outside companies to come in have been taking place for four years, the paper said.

The Journal reported that Saudis are instead offering the companies regions with less promising prospects for natural gas exploration and production. But the paper said the oil companies believe these areas wouldn't be profitable enough to warrant the required level of investment.