Bitcoin prices were trading marginally lower on Monday but had barely moved off last week’s level, which took the best-known digital currency to its highest level in three weeks.

In early trading, one bitcoin

BTCUSD, -0.28%

 was fetching $3,629.70, down 0.2% since Sunday at 5 p.m. Eastern Time on the Kraken exchange. The cryptocurrency traded above $3,700 on Friday, its highest level since Jan. 19.

Read: U.S. stock futures set for higher start as trade talks kick off, China equities rise

What are analysts saying

After bitcoin surged to its largest daily gain of the year on Friday, Nigel Green, CEO of deVere Group, a U.K. consulting firm, is warning investors to cool their excitement. He stressed the fact that bitcoin has yet to breach key resistance at $4,000 and remains well off its all-time high.

“It was a relatively sudden jump, and, of course, positive news for those holding bitcoin,” he wrote, referencing Friday. “However, the price only reached the top of the trading range and investors should not be popping champagne corks just yet.”

Green put last week’s move down as a reaction to the progress of the lightning network that is aiming to fix bitcoin’s scalability issues, the ability to process bitcoin transactions more efficiently and quickly.

Read: A team at Northwestern think they have solved one of bitcoin’s biggest problems

Altcoins and futures

Altcoins — the group of coins other than bitcoin — were trading mixed on Monday. Ether

ETHUSD, +2.47%

was the best-performing altcoin, rising 2.1% to $119.75, Bitcoin Cash

BCHUSD, -0.90%

fell 0.9% to $121.70, XRP

XRPUSD, -0.56%

was off 1% to 30 cents and after rising more than 25% on Friday, while Litecoin

LTCUSD, -4.88%

pared recent gains, falling 4.5% to $43.84.

Futures were trading lower on Monday. The Cboe Global Markets February contract

XBTG9, -0.83%

fell 0.6% to $3,605, while the CME Group February contract

BTCG9, -0.69%

was down 0.7% to $3,590. The Cboe February contract is set to expire on Feb. 13.

Read: Bitcoin hasn’t been this oversold in 4 years, chart watcher says

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