There is a new and significant presence on the Third World scene--the People's Republic of China. At meetings here of the IMF and World Bank, Finance Minister Wang Bingqian impressed everyone by the firm and articulate way in which he lined his country up with the Third World--in a way, assuming its leadership.

In doing so, Wang served notice that China in these international financial gatherings is perfectly willing to lock horns with the United States, which has never found a comfortable formula for dealing with the Third World.

The poor nations could benefit enormously from an additional source of moral support. Their demands, as articulated through the so-called Group of 24, take on such a predictably strident tone that--valid as they may be --they become counterproductive.

At the opening reception for the IMF-Bank meetings at the city hall here last week, a high IMF official, commenting on the Group of 24's "shopping list," said: "They asked for the sun, the moon and the stars, as usual. Tomorrow, we'll get our feet on the ground." He meant that when the rich nations held their own caucus, they would say "no" to the group.

A staff aide to the poor nations disgustedly waved the wordy, 36-point communiqu,e they had issued, and snapped: "I keep telling them that their job is not to produce a communiqu,e that is nothing more than a catalog, but to get action. They have a story to tell, but they don't know how to do it."

China may help. The People's Republic, a member of the IMF and World Bank only the past two years, has studiously been learning the system. This time around, Wang made three careful presentations--two of which were made public.

To the Group of 24, Wang said:

"China belongs to the Third World. We stand squarely behind the other developing countries . . . We firmly believe in both the short-term goals of the developing countries and in their longer- term objective of establishing a new international order. Uniting closely with the Group of 24, we shall strive unremittingly for the realization of our common goal."

Wang boldly pointed an accusing finger at the United States for failing "to fully honor its commitment" to the World Bank's concessional-loan affiliate.

And beyond that, he exhorted his colleagues to "close ranks, coordinate our positions and gradually work out a common strategy" to evolve a new international economic order. Taken all together, it was pretty strong stuff.

Some of the relatively affluent among the developing countries may not have been exactly comfortable with the communist Wang's rhetoric, because he went on to say they must not forget they all share "one major and prominent characteristic, namely that they were all plundered and exploited by the imperialists and colonialists in the past."

In a meeting of a joint IMF/World Bank committee designed to improve the flow of resources to poor countries, Wang, in slightly more restrained language, warned the rich countries that the poor were feeling the constraints of more severe protectionist measures.

China has been irritated from the beginning of its reopened commercial relations with the United States (and other capitalist nations) that one of its most time-honored industries, textiles, must meet severe quota restrictions despite the free-trade rhetoric cranked out of Washington and heads-of-state summits.

In recent years, India has been one of the most influential Third World spokesmen--and incidentally, a chief aid beneficiary--of the World Bank and IMF. Early on, the Indians were aware that China's entry into the IMF/Bank family would bring into their midst a big new claimant for funds.

China, of course, had isolated itself for a long time from the world community, and it is still relatively inexperienced in the ways of the international bureaucracy. But nobody who was here doubts that India and other major nations of the Southern Hemisphere not only have a new rival for funds, but for taking the strategic lead.