"If the Iranian side feels it cannot receive the money for its exported oil punctually and under desirable conditions, it will reconsider" its crude exports to India, foreign ministry spokesman Ramin Mehmanparast told his weekly press conference.
India is Iran's second largest client after China and absorbs about 20 per cent of its crude exports, but New Delhi has been struggling for more than six months to pay Tehran due to international banking sanctions imposed on the Islamic republic over its nuclear programme.
Central Bank of Iran chief Mahmoud Bahmani has estimated India's overdue crude payments at around USD 5 billion, according to the official IRNA news agency.
In early July, Iran said it had "seriously warned" Indian refineries of the possibility of a halt in oil exports because of overdue payments.
Fars news agency, quoting an unnamed Iranian oil official, said crude deliveries to India for August would be withheld unless the payment problems are resolved.
Commenting on the Fars report, Mehmanparast told AFP on Tuesday that the Iranian side "will review the issue, if there is a problem (over payments), the transaction will be halted. If there are no problems, it will continue."
Iran and India have been trying to negotiate a new payment mechanism after various Asian, Middle-eastern and European banking channels were successively closed due to international sanctions slapped on Tehran over its controversial nuclear programme.