Earlier in the day, the Union Cabinet cleared the bill that seeks to grant citizenship to non-Muslim refugees from Pakistan, Bangladesh and Afghanistan if they faced religious persecution there, sources said.
A bill to amend the the Citizenship Act, 1955, is likely to be introduced in Parliament in the next two days, the sources said.
The AIUDF firmly stands by the Assam Accord of 1985 which had fixed March 25, 1971 as the cut-off date for the detection of foreigners in Assam, said the letter, a copy of which has been sent to Assam Chief Minister Sarbanada Sonowal.
"AIUDF's clear stand is for detection and expulsion of all post 1971 foreigners from Assam irrespective of caste, creed and religion through due process of law," it said.
Assam is a "heterogeneous state" having a large number of people belonging to different tribes and castes such as Bodos, Dimasa, Tiwa, Mising, Motak, Moran, Koch-Rajbongshi, and Muslim and Hindu communities, the party leaders said.
All the communities of people are residing peacefully for centuries together but the proposed bill is "bound to disturb the peaceful existence of people in Assam", nine signatories to the letter claimed.
The letter, made available to the media here, has been signed by the party's Vice President Attwal Mazid and other office bearers.
"After partition of the country, Assam has already borne the burden of about 25 lakh registered and unregistered refugees from erstwhile East Pakistan (now Bangladesh) and this state is not in a position to bear the burden of anymore refugees," it said.
It may be mentioned here that "due to lack of industries in Assam, the state is not in a position to solve the gigantic unemployment problem and the proposed amendment shall add to the woes of the people", the letter said.