"We don't not believe that at the moment it would be helpful to provide lethal support to the Ukrainian armed forces," British Foreign Secretary Philip Hammond told a joint news conference with British Foreign Minister Jose Manuel Garcia Margallo in Madrid.
"We are clear that we cannot afford to allow the Ukrainian armed forces to collapse, though I think they are long way from that position at the moment.
"So the UK will not change its position right now on suppling lethal aid as a consequence of what is going on the ground at the moment," he added.
Hammond said the question of supplying aid to the Ukrainian armed forces was "one for individual national governments."
"It's not an EU issue or a NATO issue," he added.
Margallo called for a "frank and open dialogue" and called on Russia to respect "Ukraine's territorial integrity".
The leaders of Ukraine, Germany, France and Russia on Thursday pledged to try to save a tattered ceasefire in eastern Ukraine despite violations - including the storming of a key town by pro-Russian rebels.