Assistant Secretary of State Langhorne A. Motley gave a ringing defense of U.S. policy toward Nicaragua yesterday, telling a congressional subcommittee that Reagan administration critics "were wrong about El Salvador, wrong about Grenada and they are wrong about Nicaragua -- and for the same reasons."

Motley said that the administration policy of applying indirect military pressure on Nicaragua through aid to the rebels there may not succeed in getting the leftist Sandinista government to change its domestic and foreign policies, but that the lack of such pressure will guarantee failure.

"People and nations do not move to the negotiating table simply because it's a nice piece of furniture," he told the House Foreign Affairs subcommittee on Western Hemisphere affairs. "If anyone knows of a more effective way to create a bargaining situation with the Sandinistas, let us know."

Motley's appearance opened the administration's push for congressional passage of another $14 million in military aid to the rebels, an effort Democratic and Republican leaders have said probably will fail when it comes to a vote in March.

But Motley said, "I don't accept that judgment." He reminded the members that they had "swallowed hard" and approved a large -- and controversial -- increase in aid to El Salvador last year after prolonged debate. And he asserted that there has been "dramatic and undeniable progress" toward democracy in El Salvador.

In response to questions, Motley insisted that laws banning direct or indirect U.S. aid to the Nicaraguan rebels are being obeyed and that the United States had not encouraged any other country to pass along U.S. assistance to the rebels. "We are well aware of the intent of Congress and what the law says you can and cannot do," he said.

Motley called for stronger U.S. links to Guatemala, which he said "has confounded the traditionalists" by demonstrating a centrist majority in recent elections. He said the administration will request "roughly the same level" of economic aid to Latin nations for fiscal 1986 as it did this year, about $1.5 billion.

In response to a question from subcommittee chairman Michael D. Barnes (D-Md.), three witnesses who testified before Motley agreed that U.S. aid to the rebels should cease. Attorney William D. Rogers, who held Motley's job under President Carter, said it was "close to a dead end" and should be replaced by economic sanctions. "Force should be a last resort," he said.

Economist Norman A. Bailey, a National Security Council staff member from 1981 to 1983, agreed, saying "a different mix of measures" was required. International relations specialist Abraham F. Lowenthal of the University of Southern California said the policy hurts rather than helps peace efforts.

All three said the Latin American debt crisis has not been resolved and remains a major threat to hemispheric stability. "The real security issues are not MiGs and missiles but migration and debt," Lowenthal said.