Copenhagen's mission will be backed by laws that allow states to inspect ships suspected of posing an environmental threat.
Denmark will be tasked with inspecting and potentially blocking Russian oil tankers sailing through its waters under new European Union plans, according to reports.
The north European nation would target tankers without Western insurance, under laws that allow states to check vessels they fear pose an environmental threat.
Copenhagen's assignment comes as the West explores more ways of ensuring its $60 (€55) per barrel cap on Russian crude is met.
Western officials have admitted that “almost none” of Moscow's crude exports were sold below the $60 a barrel cap last month, the Financial Times reported on Tuesday.
Brussels' 12th package of sanctions against Russia "will include actions to tighten the oil price cap, to decrease the revenue that the country is getting from selling its oil - not to us [the EU] but to others - and fight against circumvention", EU foreign policy chief Josep Borrell said on Monday.
Instructing Denmark to inspect Russian oil tankers is likely to be one of the measures within the EU's new package of sanctions, which will be presented to member states' foreign ministers on Wednesday.
Copenhagen was chosen mainly because of its geographical location. All of Moscow's oil shipped through the Baltic Sea - which represents around 60% of the country's total seaborne oil exports - crosses the Danish straits on its way to international markets.
How would Denmark's naval inspection enforce the price cap?
G7 countries, the EU and Australia imposed its $60 per barrel cap on Russian crude exports last December due to the conflict in Ukraine.
The cornerstone of the price cap has always been the middlemen: Western insurers, shipping companies and shipowners, which are required to self-report that they are not moving Kremlin oil priced above $60.
A growing number of tankers carrying Russian crude is suspected of sailing with non-Western insurance.
Copenhagen's naval authorities would therefore be in charge of verifying if the tankers navigating its waters are abiding by the European sanctions.
The EU is also concerned that non-Western insurance might not be effective in the event of an oil spill, especially since many Russian oil shipments are being carried out on so-called "shadow fleets" of old vessels, risking a major environmental disaster.
The United Nations Convention on the Law of the Sea, which governs maritime traffic, includes clauses that allow states to "institute proceedings, including detention of the vessel" given "clear objective evidence" that the ship poses a major threat of coastal damage.