"I very much welcome the announcement by President Trump that the US is trying to find additional air defences for Ukraine," Kallas told reporters upon arrival for talks by EU leaders in Brussels.

"This is extremely important," said Kallas, who is pushing EU member states to meet a Ukrainian request for two million shells, worth five billon euros ($5.4 billion) -- having scaled back a more ambitious proposal that included air defences and missiles.

Trump made the air defence commitment in a call with Volodymyr Zelensky on Wednesday, in which the Ukrainian leader asked for help in sourcing "Patriot missile systems" in particular, according to a US readout.

"President Trump agreed to work with him to find what was available particularly in Europe," the readout said.

The offer was a rare signal from Trump that he could help bolster Ukraine's defences as he pushes for a peace deal with Russia.

Ukraine currently has seven US-made Patriot air defence systems, provided by the United States, Germany and Romania.

Officials say the system is the only one Kyiv possesses that can counter Russia's ballistic missiles.

In addition, for high-altitude interceptions, Ukraine has two European-made SAMP/T systems from Italy and France.

It has some similar systems of its own and has been provided with others for shorter-range interceptions.

Ukraine could also rely on fighter jets to intercept missiles: European allies have already given it F-16 and Mirage 2000-5 fighters.

Further Patriot systems could theoretically be available from elsewhere in Europe, but the countries hosting them have been reluctant to part with them for national security reasons.