Russia has moved more troops near Ukraine's border in recent days, despite assurances it would not attack the country's east, US Defence Secretary Chuck Hagel says.
Although Russia's defence minister had told Hagel last week that Moscow would not send troops into eastern Ukraine, "the reality is that they continue to build up their forces, so they need to make sure they stay committed to what Minister (Sergei) Shoigu told me," the Pentagon chief said after meeting his British counterpart, Philip Hammond.
But it was unclear whether the Russian defence minister carried real influence over decision-making in Moscow, given President Vladimir Putin's dominant role, the British defence secretary told a joint news conference at the Pentagon.
Hammond said "all the evidence suggests that the Russian agenda is being very much run by President Putin personally".
"And other Russian players, including Minister Shoigu, may express views, but it's a moot point, and we cannot know, we do not know to what extent all of those people are really inside the inner circle in which President Putin is planning this exercise," Hammond said.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
There are now more than 20,000 Russian troops, including airborne units, fighter aircraft and armoured vehicles, deployed near the Ukrainian border, providing ample firepower to seize the eastern region if Moscow chose to, according to US defence officials.
Hammond said diplomatic and economic sanctions against Russia over its intervention in Ukraine's Crimean peninsula were designed to isolate Moscow over its "aggression" while also deterring any further incursions.
Amid concerns among NATO states in Eastern Europe over Russia's actions in Ukraine, Hammond vowed that the alliance was fully committed to defend the sovereignty of its members.
"And I have no doubt - I don't think any member of NATO has any doubt - that all 28 members are prepared to come to the security interests, if that's what's required, to defend the integrity and sovereignty of those member countries," he said.
Asked about Ukraine's request to Washington for weapons and other lethal and non-lethal assistance, Hagel said the US administration had approved sending military rations to Kiev, while other items were still under review.
"The president's national security team is reviewing all of the other requests for assistance, particularly the non-lethal assistance to Ukraine," Hagel said.
