Chevron warned Monday that its pending $53 billion acquisition of Hess may be in jeopardy because it will require the approval of Exxon Mobil and a Chinese national oil company, which both hold rights to development of an oil field off the coast of the South American nation Guyana.

The disclosure in a filing with the Securities and Exchange Commission raised investor qualms, depressing shares of both Chevron and Hess. Chevron’s stock price fell 3% Tuesday morning before rebounding; Hess stock lost 4% of its value but bounced back slightly.

Chevron’s acquisition of Hess would add this major oil field in Guyana as well as shale properties in the Bakken Formation in North Dakota. Guyana is a country of 791,000 people that is poised to become the world’s fourth-largest offshore oil producer, placing it ahead of Qatar, the United States, Mexico and Norway. It has become a major producer in recent years, with oil giants including Exxon Mobil, China’s CNOOC, and Hess squared off in a heated competition for highly lucrative oil fields in northern South America.

Chevron said it’s been engaged in discussion with Exxon and CNOOC, aka China National Offshore Oil Co. Both companies hold rights of first refusal for decisions regarding the oil field in question, known as the Stabroek Block. Exxon Mobil operates the Stabroek Block and holds 45% interest. Hess holds 30% interest, and CNOOC holds the remaining 25% interest. Production capacity at the field is expected to reach more than 1.2 million barrels per day by the end of 2027, Exxon said in November.

If those discussions and subsequent arbitration fail to set aside those first refusal rights, Chevron said, “the merger would not close.”