Li Zhaoxing, the visiting Chinese foreign minister, and his Mauritanian counterpart Ahmed Ould Sid Ahmed told a joint news conference on Sunday that they had discussed co-operation in oil but had not signed a deal.
This comes after a Mauritanian foreign ministry official said before the talks that an oil deal was in the works.
China is in the market for new oil sources, notably in Africa, to support its rapidly expanding economy. A first delivery of Mauritanian oil was sold to a Chinese company in April.
Mauritania began producing its own oil in February, and its current unfavourable trade balance with Beijing is likely to be offset by future oil deliveries to China, observers said.
Li, who was to leave Nouakchott on Monday, met on Sunday with Ely Ould Mohamed Vall, the president, who interrupted a trip to the north of the country to "show the importance he accords to co-operation with China", Sid Ahmed said.
China has been a major supplier of modern infrastructure to Mauritania, building its first deep-water port in the 1980s.
It is now set to build a new international airport to serve Nouakchott at an estimated cost of $170 million.
Mauritania will in return supply iron ore to China.