Moscow's seizure of Crimea has caused the most serious East-West crisis since the end of the Cold War. The United States and the EU have imposed sanctions on a handful of officials from Russia and Ukraine accused of involvement in the action.
Russian President Vladimir Putin signed a treaty in Moscow on Tuesday making Crimea part of Russia again, despite Ukrainian protests and the Western sanctions.
"Looking into expanding sanctions is something that will only make the conflict worse," said Chief Executive Officer Igor Sechin, a long-standing ally of Putin, during a panel discussion at a forum for investment between Japan and Russia.
"It doesn't help solve the problem and is unproductive."
The United States imposed visa bans and asset freezes on 11 Russians and Ukrainians on Monday, including four Russian lawmakers. The EU imposed the same punishments on 21 people.
Russian forces took control of the Black Sea peninsula in late February following the toppling of Moscow-backed Ukrainian President Viktor Yanukovich by protests provoked by his decision to spurn a trade deal with the European Union last November and seek closer ties with Russia.
People in Crimea voted overwhelmingly in last weekend's referendum to join Russia.