MOSCOW/KIEV - Russia on Tuesday rejected US President Donald Trump's 50-day ultimatum to agree to an Ukraine ceasefire, dismissing the threat of "severe tariffs" as unacceptable.

Russian Deputy Foreign Minister Sergei Ryabkov emphasized that Moscow favors a diplomatic resolution to the Ukraine conflict and is ready to negotiate.

"However, if this is not met with a proper response, if we cannot reach our set goals through diplomacy, then the special military operation will go on," he continued.

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He said Moscow's position is unshakable. "We expect Washington and NATO to take this seriously."

Trump on Tuesday denied earlier allegations that he encouraged Kiev to strike deep into Russian territory, saying that he isn't taking sides in the conflict and advised Ukraine "shouldn't target Moscow" with long-range weapons.

Just one day before the clarification, Trump said at the Oval Office that the United States (US) will send weapons to Ukraine through NATO, and threatened "severe tariffs" targeting Russia if a ceasefire deal is not reached in 50 days.

He said some of the first Patriot missile systems could arrive in Ukraine "within days."

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The Russian Foreign Ministry condemned the weapon deliveries as evidence that NATO countries are not interested in peace.

US Commerce Secretary Howard Lutnick said Trump's reference to 100 percent secondary tariffs meant "economic sanctions."

Meanwhile, Ukraine's parliament on Tuesday voted to extend the country's wartime status and military mobilization for another 90 days, through Nov 5. Lawmakers also approved a temporary withdrawal from the Ottawa Convention, an international treaty that prohibits the use of anti-personnel landmines.