July 7 (Reuters) - The Indian government's communist allies, which provide the ruling coalition with a majority in parliament, could withdraw their support this week to protest against a civilian nuclear deal with the United States.
India's main opposition party, the Hindu Nationalist Bharatiya Janata Party (BJP), has already demanded a vote of confidence over the government in parliament.
But the government says it has secured support from the regional Samajwadi Party and is confident of securing a majority in case of a parliamentary vote.
The following are the most likely scenarios, according to analysts:
IF THE COMMUNIST PARTIES WITHDRAW: The left parties dispatch a letter to India's President Pratibha Patil, announcing their decision to withdraw support for the ruling coalition, led by the centre-left Congress party.
* The president calls Prime Minister Manmohan Singh and informs him of the letter and asks him to convene parliament and carry out a vote of confidence in parliament, while continuing as a caretaker government.
* Singh could try to convince the president that it still has a majority and can escape a vote of confidence -- a difficult scenario as the BJP has already demanded a vote of confidence.
* The president could also ask the BJP whether it can form a government. That possibility looks remote as the party does not appear to have the numbers and is keen on early elections.