A deactivated Titan II nuclear ICMB is seen in a silo at the Titan Missile Museum on May 12, 2015 in Green Valley, Arizona.

The two leaders of the world's nuclear club are threatening to withdraw from an arms control agreement, a move that will allow each country to bolster its arsenal with more nukes.

Russian President Vladimir Putin said Wednesday that he will develop ground-launched nuclear missiles if the U.S. withdraws from the Intermediate-Range Nuclear Forces, or INF, treaty.

The pact, signed by the U.S. and Soviet Union in 1987, prohibits the development of midrange nuclear-tipped missiles. The agreement forced each country to dismantle more than 2,500 missiles with ranges of 310 to 3,420 miles. The arms ban kept nuclear-tipped cruise missiles off the European continent for three decades.

Of the 14,500 nuclear weapons on the planet, Russia and the United States own the lion's share, with a combined total of approximately 13,350 nukes. The remaining 1,150 weapons are held by seven countries.

North Korea, the latest unwelcome addition to the world's nuke club, remains the only country to test nuclear weapons in this century.

While the exact number of nukes in each country's arsenal is closely guarded, below is a breakdown of how many weapons exist, according to estimates from the Arms Control Association and Federation of American Scientists.