American-made F-16 fighter jets due to arrive in Ukraine this summer are “no longer relevant”, a senior Ukrainian military official has said.

Ukraine’s air force is expected to take delivery of the first tranche of a dozen aircraft in July after Ukrainian pilots have been trained and the country’s airfields prepared.

Before their arrival, the Western warplanes had been held up by some as a potential war-winner that could turn the tide of the conflict in Kyiv’s favour.

“Often, we just don’t get the weapons systems at the time we need them – they come when they’re no longer relevant,” a Ukrainian high-ranking officer told the Politico news website.

“Every weapon has its own right time. F-16s were needed in 2023; they won’t be right for 2024.”

Ukrainian forces are being beaten back by their Russian enemy across almost the entire 600-mile front line – a situation blamed on worsening ammunition shortages, partly caused by a blocked $60 billion US aid package.

This has increased calls by Kyiv for more traditional weapons, such as air defence interceptors, artillery howitzers and shells.

“We need howitzers and shells, hundreds of thousands of shells, and rockets,” the officer said, estimating that Ukraine needed four million shells and two million drones.

Ahead of his arrival in Brussels for a meeting to mark the 75th anniversary of Nato, Dmytro Kuleba, the Ukrainian foreign minister, called for Kyiv’s Western allies to prioritise sending more US-made Patriot air defence batteries.

“Seven Patriot systems would be optimal, but let me be modest,” he said. “With five Patriot batteries, we can defend the main industrial cities against Russian missiles.”

The US, Netherlands and Germany have so far contributed several of the systems, which are estimated to cost about $1 billion each.

“And once we’ve taken the threat away, the Patriots go back to where they were stationed.”

But after a meeting with his Polish counterpart, Radek Sikorski, Mr Kuleba upgraded his demand to “all Patriot batteries available around the world that can be provided to Ukraine must be delivered to Ukraine”.

“Ukraine is currently the only country in the world that defends itself against ballistic missile attacks almost every day,” the Ukrainian official added.

At their meeting in Brussels, Nato foreign ministers are discussing a $100 billion, five-year military aid package for Ukraine.

The Telegraph reported on Tuesday that the scheme, dubbed Nato Mission Ukraine, was being drawn up to shield Kyiv from the “winds of political change” in the United States.

Jens Stoltenberg, the alliance’s secretary-general, told reporters on Wednesday: “What is obvious is that we need new and more money for Ukraine and we need it over many years.”

He went on to warn again that the political dispute in the US Congress was helping Vladimir Putin’s forces seize Ukrainian territory.

“That’s one of the reasons why the Ukrainians have to ration the number of artillery shells, why they have problems standing up against the Russian force with overwhelming military power because they’re able to outgun them with more ammunition and more artillery,” Mr Stoltenberg said.

Meanwhile, Volodymyr Zelensky, the Ukrainian president, has warned Russia is preparing to mobilise 300,000 soldiers by June.