By Ethirajan Anbarasan
Iran insists it wants civilian nuclear power, not weapons
In the run up to the voting on Iran at the International Atomic Energy Agency (IAEA), Indian leaders maintained that diplomacy should be given a chance before referring Iran's nuclear activities to the UN Security Council.
It appeared that India was opposed to the European Union-sponsored resolution.
But in a surprise move, Delhi voted in support of the resolution, paving the way for Iran to be referred to the Security Council.
The Indian government is now feeling the heat as its Communist allies and opposition parties are demanding an explanation for the diplomatic turnaround.
Leaders of India's left-wing parties met Prime Minister Manmohan Singh to express their strong disapproval.
"We categorically told the prime minister that India should not have voted against Iran and this action has diminished India's standing among the developing and non-aligned countries," Doraiswamy Raja, secretary of the Communist Party of India (CPI), told the BBC.
The CPI is among the left parties whose support is crucial for the survival of governing United Progressive Alliance (UPA), which the Congress party leads.
Left leaders say that they were not happy with the prime minister's explanation and will soon decide on their next course of action.
The main opposition Bharatiya Janata Party (BJP) has also criticised the government, saying its decision was believed to be due to the US pressure.
Like the Communist parties, many believe the government's decision could have been influenced by the growing India-US relations.
After decades of mutual suspicion, both countries reached a landmark nuclear deal in July this year and the pact allows Washington to help India's civilian nuclear programme.
However, the deal is yet to be ratified by the US Congress.
Following increasing criticism, Indian foreign ministry officials took pains to argue that their decision was not due to the US pressure and there was no radical shift in India's foreign policy.
Instead, they said, Delhi's decision was aimed to benefit Iran as they had persuaded the European countries not to refer Tehran to the UN Security Council immediately and that a final decision would be taken only in November.
India would import 5m tonnes of Iranian gas a year for 25 years
"As India stated earlier, there is still chance to find a diplomatic solution to the Iran nuclear issue," says veteran Indian strategic affairs analyst K Subramanyam.
But it looks like the damage has been done.
Apart from mounting criticism at home, Iran has also expressed its displeasure regarding India's position.
"We have good deep relations with India .. and their behaviour at the IAEA was strange and we didn't expect them to vote against Iran," Ali Aghamohammadi, spokesman for the Iranian Supreme Council of National Security, said.
However, Iranian officials have denied reports that the proposed natural gas export deal between the two countries would be called off due to the recent developments.
Both countries have signed an agreement worth $22bn for which Iran would supply five million tonnes of gas a year to India.
India is struggling to meet its energy demands. It currently imports 70% of the crude oil it needs and its energy demands, both in oil and gas, are expected to double by 2020 as the country's economy grows rapidly.
Nuclear energy could not be a substitute as it accounts for only 2.7% of India's total energy production.
For whatever reasons, if the gas deal with Iran fails to go through it could spoil India's much-hyped oil diplomacy.
So India needs energy-rich countries like Iran and at the same time Tehran also needs to find markets for its abundant energy resources.
It appears that both countries are now trying to play down the impact of what happened in Vienna.
But analysts say long-term implications cannot be ignored.
"India has the right to vote for anyone. But the way it went about in this issue is debatable. This will definitely have an impact on India-Iran relations," says PR Kumaraswamy, a Middle East expert at the New Delhi-based Jawaharlal Nehru University.