that should be the simla agreement. It was talked about in length in this forum many times over.
from wiki (does any Indian member have official source of the Simla agreement so I can go over the content?)
"
Both countries will "settle their differences by peaceful means through bilateral negotiations".
[1][4] India has, many a times, maintained that Kashmir dispute is a bilateral issue and must be settled through bilateral negotiations as per Simla Agreement, 1972 and thus, had denied any third party intervention even that of United Nations.
[5]
The agreement converted the cease-fire line of 17 December 1971 into the
Line of Control (LOC) between India and Pakistan and it was agreed that "neither side shall seek to alter it unilaterally, irrespective of mutual differences and legal interpretations".
[1][3] Many Indian bureaucrats have later argued that a tacit agreement, to convert this LOC into international border, was reached during a one-on-one meeting between the two heads of government. However, Pakistani bureaucrats have denied any such thing.
[2][3] This identification of a new "cease-fire line" by both the states has been argued by India as making
United Nations Military Observer Group in India and Pakistan insignificant. As according to India, the purpose of UNMOGIP was to monitor the cease-fire line as identified in
Karachi agreement of 1949 which no longer exists. However, Pakistan have a different take on this issue and both countries still host the UN mission.
[5]"