President Vladimir Putin has backed a plan to boost troop numbers by one third as he vowed to give the Russian military whatever it needs to keep up the fight in Ukraine.

In a sign the 10-month war was nowhere near over, Mr Putin and his defence chief Sergei Shoigu also announced Russia was honing its nuclear missiles and accelerating its weapons program.

It comes as Ukraine President Volodymyr Zelensky landed in the US on Thursday morning (AEDT) on his first overseas trip since the conflict began.

Mr Zelensky will later address the US Congress after meeting US President Joe Biden at the White House.

Co-inciding with Mr Zelensky’s high-security trip, the US promised a new US$1.8 billion security package ($2.76 billion), which would include the Patriot Defence System to intercept Russian missiles.

It’s the first time America has offered one of its most advanced systems which can bring down cruise missiles, short range ballistic missiles, and aircraft “at a significantly higher ceiling”.

It typically includes launchers along with radar and other support vehicles.

US President Joe Biden welcomes Ukraine President Volodymyr Zelensky to the White House. Photo: Getty

Meanwhile Mr Putin said Russia’s Sarmat intercontinental ballistic missile — dubbed ‘Satan II’, and capable of mounting nuclear strikes against the US — would be ready for deployment in the near future.

At an end-of-year conference of Russia’s top military brass, Mr Putin and Mr Shoigu made it clear they blamed NATO’s expansionism in the region for Russia having to boost its military might.

“Given NATO’s desire to build up military potential near the Russian borders, as well as to expand the alliance through Finland and Sweden, retaliatory measures are required to create an appropriate grouping of troops in north-western Russia,” Mr Shoigu said.

Russia to boost troops

Mr Shoigu proposed beefing up the armed forces to 1.5 million combat personnel from 1.15 million.

He said 695,000 of the fighters should be professional contracted soldiers — as opposed to conscripts serving mandatory military service.

Mr Putin had already signed mid-year for troop numbers to be increased by 137,000 from January 1 to reach the 1.15 million level, and has also drafted more than 300,000 reservists in a controversial mobilisation drive to support Russia’s invasion of Ukraine.

The United States and western military analysts say tens of thousands of Russian soldiers have died in the 10 months since Moscow invaded Ukraine.

On September 21 — the last time an official tally was shared publicly — Shoigu said 5,937 Russian soldiers had been killed there.

Mr Shoigu also proposed raising the age range for mandatory Russian military service to cover Russian citizens aged 21-30.

Under the current system, Russians aged between 18-27 can be called up for mandatory military service — though Mr Shoigu and Mr Putin have repeatedly said that conscripts are not being sent to fight in Ukraine.

Putin promises unlimited resources

Mr Putin promised the Russian army whatever it needed to prosecute a war nearing the end of its 10th month.

He said there were no financial limits on what the government would provide in terms of equipment and hardware.

“We have no funding restrictions. The country and the government are providing everything that the army asks for,” he said.

Mr Putin acknowledged, not for the first time, that the call-up of 300,000 reservists that he ordered in September had not gone smoothly.

“The partial mobilisation that was carried out revealed certain problems, as everyone well knows, which should be promptly addressed,” he said.

Russia’s President Vladimir Putin has promised his military whatever it needs. Photo: Getty

He also referred to other unspecified problems in the military and said that constructive criticism should be heeded.

“I ask the Ministry of Defence to be attentive to all civilian initiatives, including taking into account criticism and responding correctly, in a timely manner,” he said.

Russia occupies a huge swathe of eastern and southern Ukraine along a front stretching some 1100 kilometres but has suffered a series of defeats that have swung the war’s momentum.

Even pro-Kremlin war bloggers have expressed anger and dismay at the performance of Russia’s generals, the chaotic conduct of the mobilisation and the ceding of territory Russia had captured – most notably last month when it pulled out of Kherson, the only provincial capital Russia had captured since beginning the invasion.

Hailing Russian soldiers and defence chiefs as “heroes”, Mr Putin said Russia needed to take special note of the importance of drones in the conflict.