KARGIL, India (AP) - Pakistani shells slammed into an oil tanker convoy on a strategic highway Tuesday while Indian troops and Islamic fighters battled over mountain peaks in the disputed ®ion of Kashmir. The shelling came two days after President Clinton met with Pakistani Prime Minister Nawaz Sharif and raised hopes of a speedy end to the two-month-old battle in the snowcapped Himalayas. U.S. officials said Sharif and Clinton agreed Pakistan-based fighters would withdraw from the Indian part of Kashmir. But India says there has been no sign of            withdrawal and no letup in the shelling from both sides of the 1972 cease-fire line that divides Kashmir between the two nuclear powers.