By Olivia Le Poidevin GENEVA, Feb 6 (Reuters) - The U.S. on Friday called for a new arms control agreement after the treaty that set caps on Russia and the U.S.'s strategic nuclear weapons deployments for more than two decades expired on Thursday.

Beijing urged the U.S. and Russia to act soon, saying the global nuclear order was on the line.

Beijing, Moscow and shaken American allies are seeking new warheads as President Trump ends more than a half century of nuclear arms control with Russia.

For more than five decades, the United States and Russia (and before it, the

Russia launched a combined drone and missile attack on Ukraine early on Tuesday, knocking out power and heating supplies to thousands of apartment buildings in Kyiv amid freezing temperatures, Ukrainian officials said.

It’s worth looking at high-assay low-enriched uranium, or HALEU, specifically. This fuel is enriched to higher concentrations of fissile uranium than conventional nuclear fuel, with a proportion of the isotope U-235 that falls between 5% and 20%. (In conventional fuel, it’s below 5%.)

A ceremony has been held to mark the start of construction of the reactor building's foundation for Hungary's Paks II nuclear power plant.  ;

China has firmly rejected U.S. calls to join nuclear arms control talks with Russia, particularly following the recent expiration of the New START treaty. This development leaves the U.S. and Russia without binding limits on their nuclear arsenals for the first time in decades.