WASHINGTON — The United States and Europe are mulling additional economic sanctions on the Bashar al-Assad regime and on Russia for its role supporting the Syrian regime's assault on rebel-held eastern Aleppo, as the prospect of direct US military action to coerce an end to the bombardment recedes.

“Let me make it clear: We are considering additional sanctions,” Secretary of State John Kerry said at a news conference in London Oct. 16. “President [Barack] Obama has not taken any options off the table at this point in time. So we’ll see where we are in the next few days in the context of the discussions we’re having.”

“I think the most powerful weapon we have at the moment is our ability to make President [Vladimir] Putin and the Russians feel the consequences of what they are doing,” British Foreign Secretary Boris Johnson said at the news conference with Kerry, after hosting a meeting on the Syrian crisis with European, Turkish and Arab ministers.

“And there are a lot of measures that we’re proposing to do with extra sanctions on the Syrian regime and their supporters, measures to bring those responsible for war crimes before the International Criminal Court,” Johnson said. “These things will eventually come to bite the perpetrators of these crimes.”