A former parliamentarian and candidate for south Kashmir's Anantnag assembly seat, Beg said he extended his unconditional support to Sayeed but asserted he would not join the Peoples Democratic Party (PDP).
"If we have to stop the march of the RSS and the BJP in Jammu and Kashmir, we must strengthen the hands of (PDP patron) Mufti Muhammad Sayeed," Beg told reporters in Anantnag town.
Beg's decision to withdraw from the assembly election is seen as a serious jolt to the ruling National Conference.
Beg was the National Conference candidate in the 2014 Lok Sabha election but lost by over 40,000 votes to PDP president Mehbooba Mufti from Anantnag.
The Jammu and Kashmir elections are due in November-December.