Flattery and pressure — coupled with President Trump’s growing dissatisfaction with President Vladimir V. Putin — have helped build momentum for new economic punishments.

Despite Russia’s struggling wartime economy, which faces high interest rates and a growing labor shortage, the international sanctions regime imposed on Moscow remains largely ineffective due to tepid enforcement.

A bipartisan U.S. bill that would hit Russia with sanctions in a bid to pressure Moscow into good-faith peace negotiations with Ukraine has gained momentum this week in Congress, but it still lacks the presidential push it needs to get over the finish line.