Russia and China warned on Wednesday that Donald Trump’s proposed “Golden Iron Dome for America” missile defense system would destabilize global security and turn outer space into a new arena for armed confrontation.

“The recently announced large-scale ‘Golden (Iron) Dome for America’ program is deeply destabilizing,” the two sides said in a joint statement during a visit by Chinese President Xi Jinping to Moscow. The U.S. plan “explicitly provides for a significant strengthening of the arsenal for conducting combat operations in space,” it added.

The remarks came as Xi and Russian President Vladimir Putin celebrated the 80th anniversary of the end of World War II. Trump announced the missile shield plan in March, citing Israel’s Iron Dome as inspiration — though experts note that defending the entire U.S. would be vastly more complex and costly than protecting a country the size of New Jersey.

Moscow and Beijing also said nuclear states must “reject Cold War mentality” and avoid seeking military superiority “at the expense of the security of other States.”

According to the Russian press agency, 26 documents were signed during the meeting, including a joint declaration on strengthening cooperation on supporting international law.

After nearly four hours of talks, Xi described his meeting with his Russian counterpart as “in-depth, friendly and fruitful.” Putin said the talks were “warm and substantive,” and claimed ties between Russia and China were stronger than ever before.

Flights into Moscow were disrupted Wednesday after Ukrainian drone strikes forced airport closures ahead of Friday’s Victory Day parade.