Russia’s nuclear shield should be strengthened in coming years due to the “colossal threats” facing the world's biggest nuclear power, the head of Russia’s state nuclear corporation said on Thursday.

Russia and the United States are upgrading their nuclear arsenals - including the systems used to detect and intercept incoming nuclear-armed missiles - just as China ramps up its own nuclear capability far beyond those of Britain and France.

"Now, in the current geopolitical situation, is a time of colossal threats to the existence of our country. Therefore, the nuclear shield, which is also a sword, is a guarantee of our sovereignty," Russian state news agency RIA cited Alexei Likhachev as saying.

"We understand today that the nuclear shield must only be improved in the coming years."

US President Donald Trump in May unveiled plans for a so-called "Golden Dome" missile defence shield, inspired by Israel's land-based Iron Dome defense shield, that would cost at least $175 billion.

The US dome would aim to intercept a range of missiles - including ballistic, hypersonic and cruise - and is aimed at blocking threats from Russia and China. However, military experts agree that no such shield can intercept all missiles, especially in the quantity that either Moscow or Washington could launch.

Russia has about 4,300 stockpiled and deployed nuclear warheads and the United States has about 3,700, a total of about 87% of the world's total inventory, according to research by the Federation of American Scientists.

China is the world's third largest nuclear power with about 600 warheads, followed by France with 290, Britain with 225, India with 180, Pakistan with 170, Israel with 90 and North Korea with 50, according to the research.