The resignation of Antonio Ortiz Mena, president of the Inter-American Development Bank, is likely to cause new strains between the United States and its Latin American neighbors over control of the IDB, a 44-nation institution that provides development aid to Latin America.

IDB officials said that Ortiz Mena's resignation was spurred at least in part by the U.S. Treasury's continued refusal to allow an increase in the bank's funds until the United States obtains near-veto power over IDB loans. The United States is the IDB's largest source of financing.

Both the Treasury and Ortiz Mena are seeking to defuse tensions arising from the episode, which began Thursday with the IDB president's surprise announcement that he intends to leave his post Feb. 29. In his letter of resignation, Ortiz Mena, 75, attributed his decision to a desire to return to his native Mexico after 17 years at the IDB's helm.

But the New York Times reported Friday that Ortiz Mena quit because of the Treasury's plans to name a department official -- one of the most prominent critics of the bank's lending policies -- as executive vice president of the IDB. The post of executive vice president is traditionally held by an American designated by the U.S. government.

The official tapped by Treasury for the IDB's No. 2 spot is James W. Conrow, deputy assistant secretary for developing nations. Conrow has been the driving force behind efforts by Treasury Secretary James A. Baker III to gain more control over the IDB. The Treasury has complained that the bank's lending practices are too lax because voting power is concentrated among recipient nations rather than donors.

IDB sources said that Ortiz Mena denied the Times story at a huge meeting of IDB employes Friday afternoon in the bank's lobby. Sources present at the meeting quoted Ortiz Mena as saying that he wasn't worried about the prospect of Conrow's joining the bank's staff because people who become IDB employes shed their national loyalties and become international civil servants.

A Treasury spokesman, meanwhile, expressed the department's "very best" wishes for Ortiz Mena and said: "Our understanding is that Ortiz Mena's decision to resign is not at all related ... to Treasury's decision" to nominate Conrow.

But one official at the bank said the Conrow nomination had made it clearer than ever to Ortiz Mena that the gulf between the United States and Latin America couldn't possibly be bridged in the near future. Ortiz Mena had been reaching that conclusion over a period of months, this official said, and with Conrow coming on board "he saw that the U.S. was toughening its position even more."

One U.S. official contended that the picture was subtler. Ortiz Mena would never resist the United States' right to name a person of its choosing to the bank's No. 2 post, this official said, because "everyone knows it's the U.S.'s call."

According to this official, Ortiz Mena had been planning to resign once the bank had obtained a replenishment of its funds from member countries, so that he could hand the bank in good shape to a successor, who will be chosen by the bank's executive board. "He's old enough {to retire}; he's a millionaire; he has a hundred grandchildren," this official said. But in recent months, this official said, the prospect of new financing became increasingly remote as the United States and Latin governments battled over the issue of voting power.