Ukraine will move quickly to expand domestic arms production, aiming to meet half of the country's weapons needs within six months as it seeks to push back Russia's invasion, Ukrainian President Volodymyr Zelenskyy said.

Meanwhile, Switzerland announced Thursday that the U.S. Department of Defense had informed it that Washington is diverting a Swiss order for Patriot air defense systems to support Ukraine, which urgently needs to strengthen its defenses against increasingly intense Russian aerial attacks.

Patriot air defense systems for Ukraine

The Swiss Defense Ministry, which ordered five Patriot systems in 2022, said Thursday that it has been informed by the U.S. Defense Department that the delivery will be reprioritized to support Ukraine.

It was not immediately clear whether the Swiss-ordered Patriots would go directly to Ukraine or would replace units in other European countries that may be donated to Kyiv.

Delivery to Switzerland of the systems, worth billions of dollars, was scheduled to begin in 2027 and be completed in 2028. But the Swiss government said Washington informed it of the delay on Wednesday, adding that it was unclear how many systems would be affected.

It remains unclear when the promised U.S.-made weapons, especially the Patriot systems, might reach Ukraine. Trump has agreed to send the weaponry, but it will be paid for by European countries.

No timeframe for foreign weapons delivery to Ukraine

The U.S. Ambassador to NATO, Matthew Whitaker, said he couldn't give a timeframe for when Ukraine might get extra foreign weapons.

“We are all moving with haste to facilitate this and get this done. Things are actually moving very quickly, but I can't verify a date that this will all be completed. I think it's going to be an ongoing movement," he told reporters in Brussels.

“The plan is that there will be American-made defense equipment, capabilities, that will be sold to our European allies, that they will provide to Ukraine," he said.

British Defense Secretary John Healey said Thursday he and his German counterpart Boris Pistorius will chair a meeting of Ukraine's allies on Monday to discuss U.S. President Donald Trump's weapons plans. Healey said U.S. Defense Secretary Pete Hegseth and NATO leader Mark Rutte will attend the meeting of the Ukraine Defense Contact Group.

NATO's Supreme Allied Commander Europe, Gen. Alexus Grynkewich, said on Thursday that "preparations are underway" for weapons transfers to Ukraine and that NATO is working "very closely" with Germany to transfer Patriot systems.

Grynkewich said at a military event in Wiesbaden, Germany, that he had been ordered to "move (the weapons) out as quickly as possible." He said the number of weapons being transferred is classified.

Russia warns nuclear doctrine

A NATO attack on Russia's Baltic enclave of Kaliningrad would trigger an appropriate response from Russia, including measures prescribed by its nuclear doctrine, warned Leonid Slutsky, the chairman of the international affairs committee of the Russian State Duma.

"An attack on the Kaliningrad Region will mean an attack on Russia, with all due retaliatory measures, stipulated, among other things, by its nuclear doctrine. The U.S. general should take this into account before making such statements," Slutsky, who is also the leader of the Liberal Democratic Party of Russia (LDPR), was quoted as saying by TASS.

The statement came in response to U.S. Army Europe and Africa Commander Gen. Christopher Donahue, who told Defense News that Russia's Baltic enclave of Kaliningrad is about 47 miles wide and surrounded on all sides by NATO, so the U.S. and its allies now have the ability to "take that down from the ground in a timeframe that is unheard of and faster than we've ever been able to do."

Slutsky described rhetoric about an attack on the Kaliningrad Region as "a plan to unleash World War Three with subsequent global standoff with no winners," adding that "Today, NATO poses a threat to global security and stability."

(With input from agencies)