The United Kingdom has decided to send battle tanks and armor-piercing ammunition containing depleted uranium to Ukraine, while the United States announced on Tuesday that it will speed up its delivery of tanks, moves that Russian President Vladimir Putin said will elicit a strong response.

"The UK announced not only the supply of tanks to Ukraine but also shells with depleted uranium. ... If all this happens, Russia will have to respond accordingly, given that the West collectively is already beginning to use weapons with a nuclear component," Putin told reporters on Tuesday.

The Russian leader, who met with President Xi Jinping at the Kremlin in Moscow before Xi concluded his three-day state visit to Russia on Wednesday, made the comment in response to a parliamentary answer given by UK Minister of State for Defence Annabel Goldie on Monday.

"Alongside our granting of a squadron of Challenger 2 main battle tanks to Ukraine, we will be providing ammunition, including armor-piercing rounds that contain depleted uranium. Such rounds are highly effective in defeating modern tanks and armored vehicles," Goldie said.

Russian Defense Minister Sergey Shoigu warned that sending Ukraine depleted uranium rounds would bring the world closer to a "nuclear collision" between Russia and the West.

In a Twitter post on Tuesday, the UK's Heritage Party wrote, "We call on the UK government to cease escalation of the Ukraine conflict and to desist from sending Challenger tanks and depleted uranium shells to Ukraine."

According to Antiwar.com, depleted uranium rounds are radioactive and linked to cancer and birth defects, particularly in Iraq, where US forces used them during the 1990-91 Gulf War and the 2003 invasion.

Independent British journalist Richard Medhust, who has nearly 233,000 followers on Twitter, said in a video: "These suits (UK lawmakers) driving around in their Bentleys, they don't represent us. It's up to us now to declare war on the war machine, war on the warmongers, war on the war profiteers, war on the war hawks."

Meanwhile, in a letter sent to US President Joe Biden on Tuesday, four Republican lawmakers requested that cluster munitions — a controversial weapon banned in 110 countries — be sent to Ukraine.

The Biden administration should not hesitate to send cluster munitions because of "vague concerns about the reaction of allies and partners, and unfounded fears of escalation", US Senators James Risch of Idaho and Roger Wicker of Mississippi, and Representatives Michael McCaul of Texas and Mike Rogers of Alabama wrote in their letter.

They urged the Biden administration to "provide Ukraine with the right type and amount of long-range fires and maneuver capability to create and exploit operational breakthroughs against the Russians".

"Providing DPICM (dual purpose improved conventional munitions) will allow Ukraine to compensate for Russia's quantitative advantage in both personnel and artillery rounds, and will allow the Ukrainian Armed Forces to concentrate their use of unitary warheads against higher-value Russian targets," the letter said.

The Pentagon said on Tuesday that it is speeding up its delivery of Abrams tanks to Ukraine, opting to send a refurbished older model that can be ready faster, with the aim of getting the 70-ton machines to the conflict zone by the fall.

The original plan was to send Ukraine 31 of the newer M1A2 Abrams, which could have taken a year or two to build and ship. But officials said the decision was made to send the older M1A1 model, which can be taken from army stocks.

"It is about getting this important combat capability into the hands of the Ukrainians sooner rather than later," said Brigadier General Patrick Ryder, Pentagon's press secretary.

In January, the Biden administration had announced that it would send the tanks to Ukraine, after saying for months that these were too complicated and too difficult to maintain and repair.

The decision was part of a broader political maneuver that opened the door for Germany to announce it would send its Leopard 2 tanks to Ukraine, and allowed Poland and other allies to do the same.

Ryder, speaking at a Pentagon news conference, said the tanks will be refurbished and refitted to make them combat-ready for Ukraine.

Ukrainian leaders have been pressing for the Abrams, which were first deployed in 1991 and have a thick armor, a 120-mm main gun, armor-piercing capabilities and advanced targeting systems.