Nato members prepare for annual summit in Lithuania

Nato leaders are gathering for their annual summit this week in Vilnius, Lithuania (Virginia Mayo/AP/PA)

As the Russian invasion of Ukraine continues with no end in sight, Nato’s much-celebrated unity faces fresh strains when leaders gather for their annual summit this week in Vilnius, Lithuania.

The world’s biggest security alliance is struggling to reach an agreement on admitting Sweden as its 32nd member.