An international court is due to rule in a contentious case brought by India to try and save a retired Navy officer on death row in Pakistan for spying.
India denies Kulbhushan Jadhav is a spy. It has argued in the International Court of Justice (ICJ) that Pakistan has violated international law by forbidding consular access to him.
The rulings of the ICJ are binding but it has no power to enforce them.
The verdict is likely to fuel tensions between the nuclear powers.
India and Pakistan went to the brink of war in February over the disputed territory of Kashmir.
The neighbours have a long history of diplomatic spats and Delhi and Islamabad often accuse each other of sending spies into their territories.
The case of Kulbhushan Jadhav has been a thorny issue since he was arrested in March 2016.
Pakistan said it detained him in the restive province of Balochistan, home to a separatist insurgency that Islamabad accuses India of backing. India said he was kidnapped in Iran, which borders the province, where he was doing business.
Shortly after his arrest, Islamabad released a video in which he was shown admitting involvement in spying.
India has always questioned the alleged confession, saying that it was extracted under duress.
In April 2017, Pakistan said he had been convicted in a military court of espionage and terrorism and sentenced to death. India then filed a case with the ICJ, which ordered Pakistan not to execute him until the case was heard and a decision reached.
While India has argued that Pakistan has violated the Vienna Convention on Consular Relations by denying access to Jadhav, Pakistan has said he is not entitled to consular access because he is a spy who illegally entered the country in order to create "unrest and instability".
The ICJ was set up in 1945 to rule on disputes between nations in accordance with international law.
The last time India and Pakistan took a dispute to the court was in 1999 when Islamabad protested against India's downing of a Pakistani navy plane that killed 16 people.
The court decided that it had no jurisdiction to rule in the dispute and closed the case.
