1. Who has nukes?

2. According to the Federation of American Scientists, the United States has an estimated inventory of 6,970 nuclear warheads, with 1,750 of them strategically deployed. REUTERS/Jung Yeon-Je/Pool

3. Russia is estimated to have around 7,300 nuclear warheads, although the total is uncertain because there is no accurate count of tactical weapons. Of these, an estimated 1,790 are strategically deployed. REUTERS/Denis Sinyakov

4. France has pared down its arsenal to approximately 300 nuclear warheads. REUTERS/Benoit Tessier

5. China is estimated to have about 260 strategic and tactical nuclear weapons, and stocks of fissile material sufficient to produce a much larger arsenal. REUTERS/China Daily

6. Britain's nuclear stockpile consists of about 215 strategic and "sub-strategic" warheads on four Vanguard-class nuclear-powered ballistic missile submarines. REUTERS/Luke MacGregor

7. Pakistan is believed to possess a nuclear inventory of 110-130 warheads. REUTERS/Stringer

8. India has formally declared itself a nuclear weapon state. New Delhi is likely to have manufactured weapons-grade plutonium for at least 100-120 warheads. REUTERS/Indian Defence Research and Development Organisation

9. Israel is widely understood to possess a sizable nuclear arsenal but maintains a policy of nuclear ambiguity. Based on estimates of the plutonium production capacity of the Dimona reactor, Israel has enough plutonium for approximately 100-200 advanced nuclear explosive devices. REUTERS/Jerry Lampen

10. North Korea tested its fourth nuclear bomb in January. REUTERS/Stringer