In a somber show of US support for Ukraine's new leadership, US Secretary of State John Kerry walked the streets on Tuesday where more than 80 anti-government protesters were killed last month and promised beseeching crowds that US aid is on the way.

Kerry met in Ukraine with the new government's acting president, prime minister, foreign minister and top parliamentary officials.

Speaking to reporters afterward, Kerry urged Russian President Vladimir Putin to stand down and said the US is looking for ways to de-escalate the mounting tensions.

The Obama administration announced a $1 billion energy subsidy package in Washington as Kerry was arriving in Kiev.

The fast-moving developments came as the US readied economic sanctions amid worries that Moscow was ready to stretch its military reach further into the mainland of the former Soviet republic.

The head of the European Union's executive arm, Jose Manuel Barroso, says the bloc is ready to provide Ukraine an 11 billion euros ($15 billion) aid package in loans and grants over the coming years.

AP