Any efforts to improve relations remained closely tied to United States willingness to honor its 1973 aid commitment to Vietnam and to Hanoi's failure to account for the whereabouts of more than 2,400 MIAs in Indochina. From the signing of the Paris agreements in 1973 until mid-1978, the Vietnamese had routinely stressed the linkage between the aid and MIA issues. Beginning in mid-1978, however, Hanoi dropped its insistence that the MIA and aid questions be resolved as a precondition for normalization and stopped linking the MIA question to other unresolved matters between the two countries. Vietnamese leaders contrasted their restraint on the MIA issue with its alleged political exploitation by the United States as a condition for normal relations. As additional signs of goodwill, Hanoi permitted the joint United States-Vietnamese excavation of a B-52 crash site in 1985 and returned the remains of a number of United States servicemen between 1985 and 1987. Vietnamese spokesmen also claimed during this period to have a two-year plan to resolve the MIA question but failed to reveal details. Although Vietnam's Sixth National Party Congress in December 1986 officially paid little attention to restoring diplomatic relations with the United States, the report of the congress noted that Vietnam was continuing to hold talks with Washington on humanitarian issues and expressed a readiness to improve relations. Although ambivalent in tone, the message was more positive than the 1982 Fifth National Party Congress report, which had attributed the stalemated relationship to Washington's "hostile policy." The improved wording was attributable to the influence of newly appointed Party General Secretary Nguyen Van Linh, who was expected to attach high priority to expanding Vietnam's links with the West. Within a few months of the Sixth National Party Congress, however, Hanoi began to send conflicting signals to Washington. In mid-1987 the Vietnamese government, having determined that cooperation had gained few concessions from the United States, reverted to its pre-1978 position linking the aid and MIA issues. The resumption of its hardline stand, however, was brief. A meeting between Vietnamese leaders and President Reagan's special envoy on MIAs, General John W. Vessey, in August 1987 yielded significant gains for both sides. In exchange for greater Vietnamese cooperation on resolving the MIA issue, the United States agreed officially to encourage charitable assistance for Vietnam. Although the agreement fell short of Hanoi's requests for economic aid or war reparations, it marked the first time that the United States had offered anything in return for Vietnamese assistance in accounting for the MIAs and was an important step toward an eventual reconciliation between the two countries.