India was to appeal to the UN's top court on Monday to order Pakistan to suspend its planned execution of an Indian national convicted of spying.
In an emergency hearing due to open at 0800 GMT, lawyers for New Delhi will urge the International Court of Justice to halt the execution of Kulbhushan Sudhir Jadhav.
Jadhav was arrested in the southwestern province of Balochistan last year and Pakistani officials claim he has confessed to spying for Indian intelligence services.
But India has denied he was a spy, and last week lodged a protest at the ICJ in The Hague accusing Pakistan of "egregious violations of the Vienna convention," the court said in a statement.
India was not informed of Jadhav's detention "until long after his arrest" and Pakistan "failed to inform" him of his rights, according to New Delhi.
India is seeking the "immediate suspension of the sentence of death awarded to the accused," the court said, adding that New Delhi had also highlighted "the extreme gravity and immediacy of the threat".
"India submits that it has information that Mr. Jadhav was 'kidnapped from Iran, where he was carrying on business after retiring from the Indian Navy'," it added.
India was to present its case on Monday morning asking the court to order provisional measures to suspend the execution until the tribunal has had time to consider and rule on the full case.
New Delhi ultimately wants the tribunal to order Islamabad to annul the sentence completely.
It also wants the ICJ, set up in 1945 to rule on disputes between nations in accordance with international law, to declare that the Pakistani military court violated the Vienna Convention by imposing a death sentence on Jadhav and broke human rights laws.
Pakistan will present its arguments to the afternoon session.
Nuclear archrivals India and Pakistan routinely accuse one another of sending spies into their countries, and it is not uncommon for either nation to expel diplomats accused of espionage, particularly at times of high tension.
But death sentences have rarely been issued in recent years.