The price cap was introduced in December by G7 countries and Washington said it would help to avoid supply disruptions by keeping Russian oil flowing, while limiting revenues for Russia's President Vladimir Putin.
Prices in excess of the cap complicate trade for Russia, which has been excluded from the international financing system by Western sanctions as Urals can only trade in dollars, the currency of international commodity trade, provided it is sold below the $60 limit. Otherwise another currency has to be used.
But the sources said that, although Urals had edged above $60 a barrel on Wednesday, the way cargoes are priced on trade over a period of time meant that when the deals are closed they could still fall beneath the cap.
International oil prices leapt above $80 a barrel this week after the Organization of the Petroleum Exporting Countries and allies, including Russia, a group known as OPEC+, announced a surprise output cut on Sunday.
Further price support came from a term agreement signed at the end of March by Russia's largest oil producer Rosneft (ROSN.MM) and India's top refiner Indian Oil Corp (IOC.NS).
Urals oil prices in Indian ports had traded at a discount of $14-$17 per barrel on DES (delivered ex-ship) basis, but the term deal had this week driven deals to a discount of $12-$14 to dated Brent or ICE Brent, two of the sources said.
For May-loading cargoes in Chinese ports, Urals discounts narrowed to $8-$9 against ICE Brent on a DES basis, from about $10-$11 per barrel for April-loading cargoes, two sources in Chinese oil market said.
The Urals oil price for a particular deal is normally calculated on the basis of a monthly or several-days average of Brent differentials.
Given current ICE Brent and dated Brent prices, Urals oil cargoes on Wednesday traded slightly above $60 per barrel on a FOB (free on board) basis in Russian western ports, according to Reuters calculations.
If international prices fall, the actual price of the deal could still be below the cap.
"It all depends on pricing. Sellers and buyers are using different benchmarks, pricing periods and freight cost varies as well, so now it's just on the verge of going above the cap, but if Brent strengthens further, we see more risks of above price cap trading", one of the sources said.
None of the sources could be named because they were not authorised to speak to the press.