The latest battleground between the bottom two of the big four U.S. national wireless carriers doesn't take place on U.S. soil. Both Sprint and T-Mobile announced plans to allow those in the United States to make calls to Cuba.

Calling itself the "first national carrier to offer affordable calling option to Cuba," Sprint announced "Sprint Cuba 20 Plus," an option designed to make calling those in Cuba easier. For an extra $10 per month, Sprint users will be awarded 20 minutes to any phone line in Cuba and can tack on extra time at 70 cents per minute.

"Affordable international calling is an important feature for our customers," said Sprint senior vice president of marketing Tom Roberts. "Sprint is the first national carrier to offer an affordable calling option to Cuba. We are continuing to expand our international offers for customers traveling abroad or while calling or texting from the U.S."

The plan also allows customers to call or text Mexico or Canada at no additional cost and discounted calling to another 180 countries.

Not to be outdone, T-Mobile unveiled its own plan of attack at cornering the Cuban-calling market, although the company did it through one of holdings, MetroPCS. Users of the prepaid service will now find that Cuba has been added to the World Calling Plan. The World Calling Plan allows consumers to place unlimited calls to landlines in over 75 countries and unlimited texts to 100s others. Those looking to call Cuba will find they have 20 minutes of monthly phone time towards either a landline or a mobile line.

Both Sprint and T-Mobile have been vying for the No. 3 spot in the U.S. wireless service market. The top two, Verizon and AT&T, are so far ahead that combining Sprint and T-Mobile still wouldn't create a company with as many subscribers as one of the them. This prompted an effort by Sprint to merge. After the deal was squashed, Sprint and T-Mobile have eyed each other fiercely, often coming out with new, almost similar plans right alongside each other.

The debate on who is winning is still up in the air. T-Mobile's eccentric CEO John Legere often claims T-Mobile is no longer No. 4, but exact numbers are hard to come by, especially when one has to factor in all the different types of wireless plans involved. Still, calling Cuba is a nice step forward in the process of opening up borders between the two nations.

For more stories like this, follow us on Twitter!