Lloyd Austin, the US defense secretary, held a call with Russian Defense Minister Sergei Shoigu on Friday in which he called for an immediate ceasefire in Ukraine, the Pentagon said.

During the call Austin also “emphasized the importance of maintaining lines of communication”, according to Pentagon press secretary John Kirby.

The call is the first time Austin had spoken with Shoigu since February 18, six days before Russia invaded Ukraine.

The call came after Republican senator Rand Paul blocked the passage of a $40bn aid bill for Ukraine on Thursday. The bill will be taken up again next week.

Russia has shown no signs of halting its aggression. On Friday the UK ministry of defence said Russia was stepping up its attacks near the cities of Izyum and Severodonetsk, in eastern Ukraine, in an attempt to “envelop Ukrainian forces”.