In celebration of International Day of Peace on September 21, Burger King is asking long-time rival McDonald's to team up and make a McWhopper that would feature the best of both fast-food companies' burgers. 

Burger King made a proposal to McDonald's in an "open letter" ad in the New York Times for them to combine the tastiest bits of their Big Mac and Whopper, to be united in one delicious, peace-loving burger they would sell on Peace Day.

If the team-up would push through, the proceeds will be donated to a non-profit group seeking to raise awareness of the International Day of Peace that will provide educational resources to thousands of schools in 131 countries. 

The would-be whopping McWhopper will be sold at one restaurant for one day with staffs coming from both companies. 

Unfortunately, McDonald's said no.

Fernando Machado, SVP for Global Brand Management at Burger King Corp., said in a statement that the invitation is more than a PR stunt.  The goal is to bring attention to Peace One Day.  "We're being completely transparent with our approach because we want them to take this seriously."

McDonald's CEO Steve Easterbrook replied on Facebook that it would be a "great idea" and "inspiration for a good cause".  But he put down the idea of making a hybrid burger such as McWhopper and offered a much more vague proposal.

According to him, they love the intention that the two brands could do something bigger to make a difference.  They also commit to raise awareness worldwide, and invited Burger King to join them in a meaningful global effort.

He also urged the rival Burger King to "acknowledge that between us there is simply a friendly business competition and certainly not the unequaled circumstances of the real pain and suffering of war", and ended his Facebook post by telling Burger King they will keep in touch and a simple phone call will do the next time.