"Dollar General can more easily justify a higher price because of the greater potential operating synergies," Erik Gordon, a professor at the University of Michigan's Ross School of Business, told Bloomberg News, adding that Dollar Tree may have incentive to come back with a counteroffer. "The acquisition would do more to transform Dollar Tree's business."
In late afternoon trading in New York, the Dow Jones Industrial Average climbed 0.99 per cent, the Standard & Poor's 500 Index gained 0.77 per cent, while the Nasdaq Composite Index rose 0.89 per cent.
On Wednesday minutes of the latest US Federal Reserve meeting, held in July, will be released and scrutinised by investors for clues about the timing of a potential interest rate increase. Eyes will then turn to Fed Chair Janet Yellen's speech at the annual Jackson Hole, Wyoming global central bank gathering.
A drop in geopolitical tensions helped too. Gains in shares of United Technologies and Visa, up 2.1 per cent and 1.9 per cent respectively, led the Dow higher.
"The Fed remains accommodative, the economy is continuing to improve, and earnings are more or less not disappointing, which is all good news," Adam Sarhan, chief executive of Sarhan Capital in New York, told Reuters.
In Europe, the Stoxx 600 finished the session with a 1.2 per cent advance from the previous close. The UK's FTSE 100 Index rose 0.8 per cent, France's CAC 40 increased 1.4 per cent, while Germany's DAX added 1.7 per cent.