The pipeline is crucial for India's energy supplies
Iran's ambassador in India says Delhi must decide soon on a multi-billion dollar gas pipeline deal or else they will talk to other countries.
Iran's ambassador in India Seyed Mehdi Nabizedeh said they were willing to offer India a limited time.
The pipeline will transport gas from Iran to India through Pakistan, and is seen as crucial to Indian energy needs.
Iran and Pakistan signed the deal in May this year. Reports say China is also interested in being a part of it.
Analysts say the pipeline could contribute to regional security as Iran, Pakistan and India would depend on each other more.
The deal has been stalled by disputes over transit fees and security issues.
"We went ahead with Pakistan and signed the agreement. But India can still be part of it. But I have told this before also that this time limit is not unlimited," news agency Reuters quoted Mr Nabizedeh as saying.
The Iranian ambassador also confirmed that China was interested in the agreement.
"Yes it is true [that China has shown interest in the deal]. We hope that this tripartite agreement is settled soon so that we do not have to talk with anyone else," he said.
The 2,600-km (1,620-mile) pipeline would initially transport 60 million cubic metres of gas (2.2bn cubic feet) a day.
The Indian government has said the project is feasible, but needs to be financially viable with assured supplies.
India has boycotted trilateral meetings since mid-2007, saying it wants to resolve the issues of transit fees and transportation tariffs with its long-standing regional rival Pakistan first.
Last year, India's Petroleum Minister Murli Deora had said they were very close to signing the deal.