The leaders of India's coalition say they will seek a parliamentary vote of confidence on 22 July.
Their decision follows the withdrawal of communist support for the Congress party-led coalition.
The communists withdrew support in protest at the Indian government's decision to push ahead with a civilian nuclear deal with the United States.
If the government loses the vote India faces early elections and the nuclear deal would probably be scuttled.
The government says the nuclear deal is needed to meet soaring energy demands, but the communists say it could give the US too much influence over India.
Under the terms of the nuclear accord, India would get access to US civilian nuclear technology and fuel.
In return, Delhi would open its civilian nuclear facilities to inspection - but its nuclear weapons sites would remain off-limits.
Prime Minister Manmohan Singh decided to hold the vote after meeting Indian President Pratibha Patil on Thursday.
A two-day special session of the lower house of parliament - the Lok Sabha - will be convened on 21 July with the confidence vote scheduled for the following day.
The Congress party hopes that it will be able to replace support given to it by the communists in parliament by receiving the backing of the regional Samajwadi party.
TIMETABLE FOR NUCLEAR ACCORD
Approval needed from IAEA, expected in late July
Consent also required from 45-member Nuclear Suppliers Group
Congress to approve deal before President Bush signs it into law
All this to happen before Mr Bush's tenure expires on 20 January 2009
But correspondents say it is still unclear if the coalition has enough votes for a parliamentary majority, as there is a chance that the nuclear deal could also lead to a revolt within the Samajwadi party.
A defeat for the government in a confidence vote in the 543-member house would trigger an early election, and almost certainly would mean the end of the nuclear pact with the US.
On Thursday India submitted plans for safeguarding its civilian nuclear facilities to the UN's nuclear regulatory body.
India is under pressure from Washington to sign the accord before the US presidential elections in November.
Critics of the deal fear assistance to India's civil programme could free-up additional radioactive material for bomb-making purposes.
Former communist allies of the Indian government formally withdrew support for it on Wednesday after it vowed to press ahead with the agreement.
The communists have 59 members in India's lower house of parliament, while the Samajwadi Party has 39 MPs.
Analysts say with the left pulling out of the governing coalition, the government only has 226 members in the 543-seat parliament, and needs 46 more for a majority.