Ukraine's President Volodymyr Zelensky is visiting the UK to meet Prime Minister Rishi Sunak.
In a tweet, he said he would meet his "friend" Mr Sunak to hold "substantive negotiations".
The UK announced on Thursday that it would supply Ukraine with the long-range missiles it had requested to fight the Russian invasion.
Mr Zelensky has been meeting Western leaders in recent days seeking to bolster support for Ukraine.