The US has imposed several rafts of sanctions on Russia over its invasion of Ukraine two weeks ago, targeting its central bank, major lenders, oligarchs and elites and President Vladimir Putin, while saying all options are on the table for additional action. Here are some ways in which the US could further increase sanctions on Russia.
Tightened sanctions on banks, companies
Experts have said the US can tighten its existing penalties on Russian banks and also expand its punitive measures to other Russian banks.
The US said last month that US banks must sever their correspondent banking ties - which allow banks to make payments between one another and move money around the globe - with Russia's largest lender, Sberbank, but did not freeze its assets.
The US also expanded the scope of existing curbs on Americans dealing in the debt and equity of Russian state-owned enterprises. The restrictions apply to 13 firms, including Gazprombank, the Russian Agricultural Bank and Gazprom.
If the US chooses to tighten its sanctions on banks and firms already hit with restrictions, it could use its most powerful sanctioning tool and add them to the Specially Designated Nationals (SDN) list. Such a move would effectively kick them out of the US banking system, ban their trade with Americans and freeze their American assets.
The US could also target large state-owned enterprises in other sectors, including in energy, mining, metals and shipping sectors, said Edward Fishman, who worked on Russia sanctions at the State Department during President Barack Obama's administration.
The US could also put large Russian companies on a trade blacklist, forcing their suppliers to seek special licenses to sell any US-made items to them. The licenses would generally be denied.
Energy
President Joe Biden on Tuesday imposed an immediate ban on Russian oil and other energy imports. The US could further tighten energy-related sanctions by adding major companies such as oil giant Rosneft or gas producer Gazprom to the SDN list.
Another avenue to tighten energy-related sanctions would be through threatening secondary sanctions against other countries buying Russian oil, Fishman said, effectively halting the purchasing of Russian oil globally.
Secondary sanctions
The US could also enforce secondary sanctions against designated Russian entities and individuals, which would threaten anyone in the world performing transactions with Russia, Fishman said.
Fishman said the first step would be to add all major Russian banks, companies and government agencies to the SDN list before "aggressively" enforcing secondary sanctions on those doing business with the designated entities.
If countries such as China, India or others help Russia undercut sanctions, Fishman said the Biden administration could come under pressure to wield secondary sanctions.
Further swift restrictions
The European Union said last week it was excluding seven Russian banks from the SWIFT messaging system that underpins global transactions, but stopped short of including those handling energy payments.
The US and its allies could further tighten those restrictions and block access of more or all Russian banks to SWIFT, the world's main international payments network. Fishman said only one major bank, VTB, had been cut off so far. "There's a lot more we could do there," he said.
Oligarchs
The US has imposed several rounds of sanctions on Russian oligarchs and elites, including metals and telecoms tycoon Alisher Usmanov and Nikolay Tokarev, the chief executive of energy giant Transneft, among others.
The US could continue to impose sanctions on Russian oligarchs who have not yet been targeted and could also take action to bring its sanctions in line with the EU or United Kingdom, which have targeted several Russian oligarchs not yet designated by Washington.
Those include Chelsea soccer club owner Roman Abramovich, tycoon Mikhail Fridman and billionaire Petr Aven. Aven and Fridman co-founded LetterOne, or L1, which has long-term investments in the technology, energy, health and retail sectors. Fridman is also the co-founder of Alfa Group, which owns Russia's top private bank Alfa Bank.
In his State of the Union address last week, Biden said the US would work to seize the yachts, luxury apartments and private jets of wealthy Russians with ties to Putin.
Financial embargo, investment ban
Another move could be to impose a total financial embargo on Russia, likely by issuing a new executive order that would bar Americans from exporting to or importing from Russia goods, services or technologies, said Brian O'Toole, a former US Treasury Department official now with the Atlantic Council think tank.
"Then Russia becomes Iran," O'Toole said.
Short of a full financial embargo, the US could also issue an investment ban that may also have a chilling effect on Russia's economy, O'Toole said, adding that it could be tricky to implement. Such a ban would bar Americans and US banks and companies from investing in Russia.
The White House on Tuesday banned new US investment in Russia's energy sector.