Several media reports over the weekend suggested Deutsche Bank CEO Christian Sewing had dropped his opposition to the deal. Sewing was reportedly forced to reconsider his stance following investor pressure over the bank's declining performance.
The German government, which still owns 15 percent of Commerzbank, is understood to be backing a tie-up between the country's two largest lenders. Reuters reported that Berlin is pushing for a deal, even though it could cause a multi-billion euro financial hole, because it would force the re-valuation of the lenders' assets.
Deutsche shares were up by over 2 percent in early deals Monday, while Commerzbank was up nearly 4 percent. Over a 12-month period, shares of both companies are down by around 40 percent.
A banking industry source with knowledge of the matter, who preferred to remain anonymous, told CNBC there's not massive support for the merger within Deutsche Bank. "The general feeling is that the merger is not a great idea since Commerzbank doesn't have the same amount of credibility on the street as Deutsche Bank when it comes to clients and this can impact future trades."
Another concern is the German government's stake in Commerzbank. "There is skepticism that a merger could mean a bigger say from the government in (the) bank's dealings," the source added.
A spokeswoman from Commerzbank declined to comment. Deutsche Bank did not immediately respond to a CNBC request for comment. However, both the companies declined to comment on the merger of a prospect to Reuters.
Reports of the possible merger have garnered reaction from across the industry, with some cautioning against the move.
"I am not too optimistic on the merger synergies. There is some room but I don't think it will have any major impact on stock prices of either banks because it's still to be proven that there are synergies. The situation is still very fluid," Michael Huenseler, head of credit portfolio management at Assenagon Asset Management, told CNBC's "Squawk Box Europe" on Monday.
"First of all, there is no sound economic reason from my perspective. There is no immediate need as there is no concern of the liquidity position ... And therefore it all boils down to whether you could create a strong bank out of the two," he said.
Huenseler added that if a merger becomes more concrete it could give a boost to both company's shares, but said there would be no great benefit in the long or medium term.
Meanwhile, the former chairman of Barclays, Gerry Grimstone told CNBC Monday that it would require a lot of "hard work" in putting together these two big banks.
"I think Germany probably wants a banking champion, but gosh, putting two big banks together is hard work," Grimstone told CNBC's Dan Murphy in Dubai.
"It's good for the competition. I think you need strong banks. If it's going to make it a strong bank it makes sense. But as I said before these aren't easy things to get right."
Speculation about a merger has been rife for months, heightening under the tenure of German Finance Minister Olaf Scholz, who has spoken out in favor of strong lenders for the European nation. Both banks have struggled to return to sustainable profitability since the global financial crisis.
While the government has made no official statement on the potential merger, speaking to CNBC at the World Economic Forum in Davos earlier this year, Economy Minister Peter Altmaier said he is willing to lend "political support" to Deutsche Bank in its recovery path.
"Deutsche Bank ... suffered some setbacks in the past, but it is basically sound and it can recover and so the question is what are the details of such strategy. And as we discussed with the CEO and the board and all the people concerned, I trust in Deutsche Bank and I will lend my political support to Deutsche Bank, " he said.
In the past few years, Deutsche Bank has made headlines for all the wrong reasons — from settlements with the U.S. Department of Justice, to management reshuffles, weak earnings, constant restructuring and steep stock price falls.
Sewing, the bank's current CEO who took the helm in April 2018, has been making efforts to turn around the bank's ailing strategy.
- Reuters contributed to the story.