Russia is laying the groundwork for the annexation of Ukrainian territory and is installing illegitimate proxy officials in areas there under its control as it seeks to exert total control over its gains in the east, the White House said on Tuesday.

Unveiling what he said was US intelligence, John Kirby, the chief National Security Council spokesperson, told a White House news briefing that the Russians are preparing to install proxy officials, establish the rouble as the default currency and force residents to apply for citizenship.

"We have information today, including from downgraded intelligence that we're able to share with you, about how Russia is laying the groundwork to annex Ukrainian territory that it controls in direct violation of Ukraine's sovereignty," Kirby said.

The same tactic was used in 2014 when Russia announced its annexation of Crimea after taking over control from Ukraine, Kirby said.

The international community considers Crimea's annexation illegitimate.

"We want to make it plain to the American people," Kirby said.

"Nobody is fooled by it. (Russian President Vladimir Putin) is dusting off the playbook from 2014."

Russia sent tens of thousands of troops into Ukraine on Feb 24 in what it calls a "special military operation" to ensure its own security.

Russia is now also attempting to take control of broadcasting towers, he said.

At the same time, Kirby said the United States in the next few days will announce a new weapons package for Ukraine as it engages Russia in fierce battles in eastern Ukraine.

It will be the 16th such drawdown of money approved by Congress and allocated under presidential authority, he said.

The package is expected to include US mobile rocket launchers, known as HIMARS, and rounds for Multiple Launch Rocket Systems as well as artillery munitions.

The Russian embassy in the United States dismissed Washington's comments as "fundamentally false".

"To date, more than 45 thousand tons of humanitarian cargo have been sent to Ukraine, the DPR and the LPR. How does all this relate to the concept of annexation?" it said in a Facebook post, referring to the Russian-backed republics of Donetsk and Luhansk.

The United States has provided US$8 billion (RM35.6 billion) in security assistance since the war began, including US$2.2 billion in the last month.

Washington will impose sanctions on officials involved in representing themselves as proxy officials, Kirby said.

He predicted these proxies to try to hold "sham referenda" seeking to legitimatize Russian control.

- Reuters