The UK has offered to deploy land, air and sea forces to bolster the defence of Nato countries on their northern and eastern borders as tensions over Russia’s military ambitions in Ukraine deepen. Boris Johnson is expected to speak to the Russian leader Vladimir Putin this week, and travel to the region, despite intense domestic pressure over a possible leadership challenge in the wake of the “partygate” scandal. Johnson said the extra resources were a sign of Britain’s commitment to its Nordic and Baltic allies, and come after the US president, Joe Biden, promised on Friday to send a small number of American troops to eastern European and Nato countries “in the near term”. The decision aimed to “send a clear message to the Kremlin”, Johnson said in a statement. “We will not tolerate their destabilising activity, and we will always stand with our Nato allies in the face of Russian hostility.” The deployments included sending two warships to the Black Sea, increasing troop numbers and supplying rocket systems in Estonia, on the Russian border, and deploying fast jets to patrol Romanian and Bulgarian airspace from a base in Cyprus, the Foreign and Commonwealth Office said. UK officials will travel to Brussels to finalise details of the military support this week. Johnson asked defence and security chiefs to step up efforts in Europe, and told his foreign and defence secretaries to travel to Moscow to meet their Russian counterparts. In the UK, chief of defence staff Admiral Sir Tony Radakin will on Tuesday brief the cabinet on the Ukrainian crisis. Top US officials on Friday urged a focus on diplomacy while saying that Russia now had enough troops and equipment in place to threaten the whole of Ukraine. Mark Milley, the top US general, warned that a Russian invasion would be “horrific” for both sides, and “result in a significant amount of casualties”. Both the US and UK have withdrawn staff and families from embassies in Kyiv, and British travel advice now warns against all but essential travel to the country. The Foreign Office is also expected to announce tougher sanctions on Monday, meaning the UK can target Russia’s strategic and financial interests – despite reported US worries over the extent of “dirty” Russian money in London.