BEIJING (Reuters) - China's Foreign Ministry on Thursday brushed off doubts about how many countries have offered support for its position in a case brought by the Philippines over Chinese claims in the South China Sea, saying the number of nations was growing daily.

China has stepped up its rhetoric ahead of an expected ruling by the Permanent Court of Arbitration in the Hague on the Philippine case. China refuses to recognize the case and says all disputes should be resolved through bilateral talks.

China says more than 40 countries have offered support for its position, the most recent being Zimbabwe and Sri Lanka.

But only eight countries have come out in public support, including land-locked nations such as Niger and Afghanistan, says Washington's Center for Strategic and International Studies.

On Wednesday, a senior U.S. official voiced scepticism at China's claim that dozens of countries were backing its position, saying it was not clear even about what those countries may have agreed to.

Chinese Foreign Ministry spokeswoman Hua Chunying said public reports showed at least 47 countries offering support, though the figure was not complete as some nations' backing had not been publicly reported.

"The number of people supporting China rises by the day, so I have no way of giving you a precise figure," she told a daily news briefing, adding that the actual number was not the most important thing.

"As long as you have an objective and impartial position, as long as you understand the main points of the history of the South China Sea and the essence of the so-called 'arbitration case', any unbiased country, organization or person will unhesitatingly chose China's just position," she said.

China claims almost all of the energy-rich South China Sea, through which more than $5 trillion of maritime trade passes each year. Brunei, Malaysia, the Philippines, Taiwan and Vietnam have overlapping claims.

The Philippines is contesting China's claim to an area shown on its maps as a nine-dash line stretching deep into the maritime heart of Southeast Asia, covering hundreds of disputed islands and reefs and encompassing a vital global trade route.

The consensus among officials and analysts is that the ruling will go largely against Beijing.

(Reporting by Ben Blanchard; Editing by Clarence Fernandez)