The source said a senior official in the State Security Council would propose the date at a session of the People's Council (Khalk Maslakhaty), the country's top representative body, Tuesday.
"This will demonstrate commitment to Saparmurat Niyazov's policy because this is a date when the country marks both the day of the national flag and the birthday of the first president," the source said.
Former Turkmen President Saparmurat Niyazov died of heart failure last Thursday at the age of 66. He ruled in an eccentric manner, erecting golden statues to himself, naming a meteorite in his name, and decreeing that his quasi-Islamic precepts, under the title of Ruhnama, be the nation's guiding principal.
The People's Council, which settles all issues in the country and has the right to amend the Constitution, is also set to submit several candidates for the presidential post at its December 26 session, according to diplomatic sources in the Central Asian country.
People in Ashgabat, the capital of Turkmenistan, said that the most probable candidate for the post is acting President Gurbanguly Berdymukhammedov, but the Turkmen Constitution prohibits an acting president to run for the post.
Moscow, which has resisted radical power changes in post-Soviet nations, said earlier it hopes power in Turkmenistan will be transferred lawfully.
But the Turkmen opposition urged the international community to support democratic elections in the country and to ensure the presence of international observers during the elections.
"Turkmen people have a historic opportunity to enter a path of democratic choice following Saparmurat Niyazov's death," the Union of Turkmenistan's Democratic Forces said in a statement, which was distributed in Kiev.
The Union also urged Turkmen authorities and citizens to prevent possible conflicts and ensure stability in the country.
The Union called for "the release of all political prisoners and the end of political repression," promising no persecution of people forced to cooperate with the dictator's regime who are ready to build a new democratic system in Turkmenistan.