White House Sending Envoy to Vietnam : Diplomacy: Retired Gen. John Vessey will assess Hanoi’s cooperation in accounting for missing U.S. servicemen. A positive report could lead to a change in policy.

In a step that could open the way to a new kind of relationship with Vietnam, the White House announced Saturday that it is dispatching retired Gen. John W. Vessey Jr. to assess whether Hanoi is doing enough to help account for U.S. servicemen missing from the Vietnam War.

Sen. Charles E. Grassley (R-Iowa), a leading critic of the Vietnam government’s efforts to resolve the issue, said he had been assured by President Clinton that “no changes in policy are implied in this visit” by Vessey to Hanoi. But it was obvious that a positive assessment by Vessey could lead to a change in policy.

The United States, for example, is under strong pressure from its major industrial allies and Asian countries to withdraw its objection to their providing bank loans to Vietnam. That objection might be lifted if Vessey finds no fault with Vietnamese cooperation.

The 70-year-old Vessey, a former chairman of the Joint Chiefs of Staff, has gone to Vietnam several times in the last few years as former President George Bush’s special envoy inquiring about missing and possibly imprisoned Americans from the war.

The White House said Vessey will be in Hanoi on April 18 and 19. Outlining one litmus test for the visit, officials said he will try to obtain guarantees of access to Vietnamese archival records on American prisoners of war and missing in action.

Grassley was quick to give his own thoughts about Vessey’s likely assessment, insisting that the Vietnamese government has not helped American officials trying to check out reports that missing Americans have been spotted.

“We continue to get field reports that Vietnam has not been cooperative with respect to live-sighting reports,” Grassley said. “There is a long way to go before a full accounting is reached. Therefore, there is no basis for optimism that the Vessey visit signals a change in relationship with Vietnam.

“As a democracy,” he added, “we are obliged to press for a full accounting of our soldiers lost in battle.”

White House officials want the Vessey assessment to reach them before the end of the month, when the International Monetary Fund decides whether to release loans to Hanoi. The United States, which does not formally recognize Hanoi, has used its weight in the IMF to stop these loans.

Some Clinton Administration officials also fear that other countries such as Japan and France, which are prepared to begin trading with and making loans to Vietnam, will sidestep the United States and gain footholds in Vietnam’s market.

Despite Grassley’s assessment, some in the Administration believe Vietnam has cooperated with the United States on missing servicemen in the last 18 months. But they are hesitant about rewarding Vietnam.

Before announcing the mission to Hanoi, the White House reportedly assured members of Congress that, even if the Vessey assessment is positive, the United States does not intend to lift its 18-year-old embargo on trade with Vietnam.