The so-called "long stop date" or the last date of the agreement expired last week, sources with direct knowledge of the matter told Reuters.
"DBS confirms that we have extended the long stop date to June 2 or such other later date as the parties may agree," a DBS spokesman told Reuters.
A Temasek spokesman also confirmed the extension.
Temasek now owns about 29 percent of Singapore-based DBS, Southeast Asia's largest bank. That will rise to about 40 percent if the Danamon deal goes through.
DBS's $7.2 billion bid to buy Danamon, Indonesia's sixth-biggest lender, has been stuck for a year due to regulatory obstacles since Bank Indonesia, the country's central bank, announced it would cap ownership stakes in banks.
Indonesia is also pressing Singapore for the need for reciprocity over foreign bank licences, adding pressure on Singapore to open up its banking sector if the DBS bid for Danamon is to go ahead.