Mr Zelensky has been pushing for permission to use Western-provided long-range missiles to target launch sites inside Russia in response, but Joe Biden, the US president, has so far vetoed the request because of risks of escalating the war into a direct Nato-Russian conflict.
Mr Lammy and Mr Blinken announced that they would travel together to Kyiv to consult with Mr Zelensky about Ukraine’s current needs this week, but refused to say whether the restrictions would be lifted.
The purpose “to hear directly from the Ukrainian leadership how they see their needs in this moment, toward what objectives, and what we can do to support them”, Mr Blinken said.
The trilateral discussions are expected to inform a summit in Washington between Sir Keir Starmer, the UK Prime Minister, and Mr Biden on Friday.
The “strategic in-depth discussion” in Washington is expected to cover both aid to Ukraine and efforts to secure a ceasefire in Gaza and reduce tensions in the Middle East.