(AFP) - British Foreign Secretary David Cameron vowed to maintain military support for Ukraine during a surprise visit to Kyiv announced on Thursday, with the West's attention focused on the Middle East.

The visit by Cameron, a former prime minister, came as Ukrainian President Volodymyr Zelensky said that the flow of vital artillery ammunition from Western allies has dropped off since the start of the war between Israel and Hamas last month.

Cameron was in Kyiv and also visited the southern port city of Odesa on his first trip abroad as foreign minister of the UK, which has been a staunch ally of Ukraine since Russia launched a full-scale invasion in February 2022.

"We will continue to give you the moral support, diplomatic support, the economic support, but above all, the military support, that you need not just this year, and next year, but for however long it takes," Cameron said during a meeting with Zelensky.

"Russia thinks it can wait this war out, and that the West will eventually turn its attention elsewhere. This could not be further from the truth," he added in a separate statement.

However, Zelensky said Ukraine was already seeing a drop off in supplies as Western allies find their resources stretched, telling him that warehouses are "empty" or that there is a "legal minimum" that must be kept in reserve.

"Our deliveries have decreased," Zelensky told reporters, referring specifically to 155-millimetre shells that are widely used on the eastern and southern frontlines in Ukraine, saying "they really slowed down".

Zelensky thanked Cameron for making the trip while the world's attention was increasingly focused on the fighting between US-ally Israel's army and Hamas.

"Now you know the world is not focused on the situation on our battlefield in Ukraine and dividing the focus really does not help," he told Cameron in a video distributed by the presidency.

- Russian missile stockpiles -

Zelensky added that the two men had had a "good meeting" that focused on "weapons for the front line, strengthening air defence, and protecting our people and critical infrastructure".

He told reporters that Russia is "accumulating" missiles to fire at Ukraine in the winter months but that Ukrainian air defense is "better than we were last winter."

There are growing reports that Ukrainian forces have gained a foothold on the eastern bank of the Dnipro river in the south of the country, raising hopes in Kyiv for substantial advances towards the occupied region of Crimea.

However, with the top Ukrainian commander recently describing the war as a stalemate, and no clear sign of a breakthrough in the frontlines, Western allies are concerned.

Ukraine's foreign ministry said Cameron also attended talks with his counterpart Dmytro Kuleba on issues related to weapon deliveries, arms production, and maritime security in the Black Sea.

The British Foreign Office said Cameron had visited the port of Odesa on Thursday -- the second day of the visit -- and hailed new measures to insure cargo ships utilising Ukraine's ports despite Russian military threats.

"This step will be of great importance for Ukraine's export earnings and its economic recovery," said Cameron, according to a Ukrainian Foreign Ministry statement.

Zelensky meanwhile highlighted efforts to restart shipping routes on the Black Sea after Russia earlier this year exited a deal safeguarding grain exports from Ukraine's ports.

"We have been able to provide such protection to the western part of the Black Sea, which now enables our maritime export corridors to operate," he told representatives of countries on the Black Sea.

In remarks to reporters, Zelensky also welcomed a summit in California on Wednesday between Chinese President Xi Jinping and US President Joe Biden, who pledged to reduce tensions. The great-power talks were "good for us," he said.

Cameron earlier met with Ukrainian Deputy Prime Minister Olga Stefanishyna, London said, to discuss Ukraine's aspirations to join the US-led NATO alliance.

"The UK is clear that Ukraine's rightful place is in NATO and is working with Allies to smooth the path to Ukraine's accession by removing the need for a Membership Action Plan," Cameron was cited as saying.

The announcement of Cameron's visit came as Ukraine's air force said air defence systems had downed 16 Russian attack drones overnight, as well as one cruise missile.

© Agence France-Presse