Global leaders are meeting in Washington on Thursday to unite against the threat of nuclear weapons around the world.

The nuclear security summit, hosted by President Barack Obama, aims to put pressure on North Korea amid concerns over its recent nuclear tests and missile launches.

Related: North Korea Says It Successfully Conducted Hydrogen Bomb Test

But many other countries, including the U.S., have known stockpiles of nuclear weapons.

More than two dozen nations have nuclear power. Only nine possess actual nuclear weapons: Russia, the United States, China, India, Israel, France, North Korea, Pakistan and the United Kingdom.

The Ploughshares Fund, a global security foundation, estimates there are more than 15,000 nuclear weapons around the world; the U.S. and Russia possess 93 percent of them. The former Cold War foes keep nearly 2,000 nuclear weapons at the ready for immediate launch against each other, according to the Nuclear Threat Initiative.

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While the exact number in each country's arsenal is often a closely guarded secret, some information is publicly available. Here's a breakdown of nuclear arsenals by country, based on data from leading experts in nuclear estimates.

Russia

Total nuclear weapons: 7,300, according to the Federation of American Scientists.

Number that are operational: 1,790

Number retired/awaiting dismantlement: 4,490

Total nuclear tests, approximately: 715, according to the Arms Control Association.

First test: August 1949

Most recent test: October 1990

United States

Total nuclear weapons: 6,970

Number that are operational: 1,750

Number retired/awaiting dismantlement: 4,670

Total nuclear tests, approximately: 1,030

First test: July 1945

Most recent test: September 1992

An unarmed Minuteman III intercontinental ballistic missile launches during an operational test at Vandenberg Air Force Base, California, on Feb. 20, 2016. U.S. Air Force via AP, file

China

Total nuclear weapons: 260

Number that are operational: 0, according to the Federation of American Scientists. All are in stockpile.

Number retired/awaiting dismantlement: 260

Total nuclear tests, approximately: 45

First test: October 1964

Most recent test: July 1996

India

Total nuclear weapons: 110 to 120

Number that are operational: 0, according to the Federation of American Scientists. All are in stockpile.

Number retired/awaiting dismantlement: 110 to 120

Total nuclear tests, approximately: 3

First test: May 1974

Most recent test: May 1998

Israel

Total nuclear weapons: 80

Number that are operational: 0, according to the Federation of American Scientists. All are in stockpile.

Number retired/awaiting dismantlement: 80

Total nuclear tests, approximately: 0. There haven't been any confirmed tests.

France

Total nuclear weapons: About 300

Number that are operational: 280

Number retired/awaiting dismantlement: 10

Total nuclear tests, approximately: 210

First test: February 1960

Most recent test: January 1996

North Korea

Total nuclear weapons: Unknown. The U.S. said in February it had intelligence indicating the secretive nation could soon have enough plutonium for nuclear weapons and was taking steps toward a long-range missile system, but experts do not believe North Korea currently has the technology to deliver weapons.

Total nuclear tests, approximately: 4

First test: October 2006

Most recent test: January 2016

Pakistan

Total nuclear weapons: 110 to 130

Number that are operational: 0

Number retired/awaiting dismantlement: all 110 to 130

Total nuclear tests, approximately: 2

First test: May 28, 1998

Most recent test: May 30, 1998

United Kingdom

Total nuclear weapons: 215

Number that are operational: 120

Number retired/awaiting dismantlement: 95

Total nuclear tests, approximately: 45

First test: October 1952

Most recent test: November 1991

Sources: Nuclear Threat Initiative; Federation of American Scientists; Arms Control Association.