World Bank officials have concluded that the bank must reshape its approach to development lending following an unexpected $2 billion drop in loan commitments.

In particular, high officials have come to the conclusion that the economic environment in the countries receiving help may be more important than the actual projects being put in place. They cite as an example the fact that Mexico's per capita income is not expected to return to the 1980 level before 1990 despite that nation's highly touted recovery.

"Countries are littered with good projects, where they didn't have the proper supporting environment," one informed source said.

The need for better growth rates in Third World countries, at a time when private bank and official bilateral sources of development money are drying up, explains the bank's dismay at its seeming inability to help fill the breach.

The bank's examination of both its qualitative and quantitative performance has been accelerated by the decline in its new loan commitments compared with expectations. Against a projection -- now labeled within the bank as "a poor forecast" -- of loan commitments in the range of $12.6 billion to $13.3 billion this year, the actual total will be about $11 billion.

It was the second consecutive year in which commitments trailed the goal: In fiscal 1984, commitments were $11.95 billion, compared with the projection of $12 billion to $12.6 billion. Actual disbursements of loan money are still on target, but will begin to slip unless the commitment trend is reversed.

World Bank President A. W. Clausen had revealed these numbers to the bank's executive board at the end of 1984, bringing into question whether it would be politic for the bank to recommend a large new general capital increase (GCI), as had been planned.

Reliable sources indicate that while Clausen will not bring up the question of a capital increase at the International Monetary Fund/World Bank Development Committee meeting here in April, discussions will be started on the size of a GCI at board meetings this summer. Clausen is expected to make a strong pitch for a GCI at the annual meetings in Korea early in October.

The rationale will be that despite the unexpected shortfall in commitments this year, there will be a resumption of commitment activity in the years ahead. The result is expected to be a combined three-year commitment total of $35 billion to $40 billion for the period from 1985 through 1987. This is compared with about $32 billion for the period from 1982 through 1984. By 1987, according to some calculations at the bank, the annual commitment rate will be $16 billion to $17 billion, or about 50 percent greater than the current level.

But policy-makers at the bank concede that if the bank's role in Third World development is to grow to such a degree, the quantitative result will have to be supported by qualitative changes. This may imply a relaxation of the bank's current stringent tests for creditworthiness of the borrowers -- tests that in part explain the 1985 shortfall in commitments.

The bank also may have to review specific loan limits. For example, no one country is supposed to have more than 10 percent of the bank's total loans -- a ceiling that has slowed assistance to Brazil. No four countries are supposed to have more than 33 percent. And the bank's so-called "structural adjustment loans," which allow the bank to make money available for help outside of specific projects, are limited to 10 percent of the total.

All of these rules have inhibited the bank's effectiveness, according to analysts in and out of the bank. Demands for changes in approach have been loudly articulated by Third World clients, and others, in recent years.

Although no decisions have been reached on questions such as relaxing standards for creditworthiness, some tentative conclusions have been reached:

* The bank must have a more individualized approach to development lending than it had 20 years ago because there is a greater diversity among its client-states. They now run from the more dynamic countries such as Korea and Thailand at one extreme, to depressed, underdeveloped African nations at the other. And in between, there are the middle-income countries such as India, China, Mexico and others that have different debt loads.

* There must at the same time be a greater concentration of effort in the least developed countries; the attention to the African continent is an example of how the bank must use resoures.

* The bank and its officers have to be weaned further away from project lending, which still accounts for 75 percent of all loans, because "good projects and poor policy don't make sense."

* In some countries, the bank should abandon all new project lending, and concentrate (as it now is doing in the sub-Sahara region) on rehabilitation and maintenance of what is already in place. This, in particular, is one lesson that has been learned from the 1985 shortfall, which showed that some countries quit asking for bank money because they couldn't put up their own share of the new investment.

* There must be coordination between the bank and the IMF, which often work at cross-purposes. The reason: the bank's bias is for development, the IMF's for financial stabilization. Often, the country is caught between two competing bureaucracies.