LONDON (Reuters) - Ether was set for its largest two-day gain in nearly two years and bitcoin approached a record high on Tuesday on speculation about the outcome of applications for U.S. spot exchange-traded funds that track the world's second-biggest cryptocurrency.

Ether, which underpins the ethereum blockchain network, was 4.4% higher on the day at $3,650, after jumping 13.7% on Tuesday.

Top cryptocurrency bitcoin was last up 2% at $70,850, around 4% shy of its March peak of $73,803.25.

The U.S. markets watchdog will give its ruling on some spot ether ETF applications this week. Analysts and investors said Tuesday's jump was a result of unconfirmed talk that the Securities and Futures Commission might approve these products, after investors had previously thought they would be rejected.

Bitcoin rallied sharply earlier this year after the SEC gave approval to several spot bitcoin ETFs, which have seen billions of dollars in inflows.

So far in 2024, bitcoin has gained 67%, but ether is now close behind, with a gain of 60%.

"Ethereum has taken poll position in the latest crypto rally ahead of Thursday's first final SEC deadline to decide on an ETH ETF," said Ben Laidler, global markets strategist at eToro, using ether's market ticker.

"Outright approval is a long shot, but any guidance on a pathway to eventual acceptance would be a big step forward."

VanEck, ARK Investment Management and seven other issuers have filed with the SEC to list spot ether ETFs. The SEC must decide on VanEck's and ARK's filings, which are first in line, by May 23 and May 24 respectively

Joseph Edwards, head of research at Enigma Securities, cited reports saying the SEC had asked exchanges that would list the ether ETF to update their filings and separate Bloomberg ETF research that showed analysts have raised their informal probabilities of approval.

The SEC did not immediately respond to an emailed request for comment sent outside U.S. office hours early on Tuesday.

"Opposing the ETH ETF after the BTC one was approved always seemed like an odd case for the SEC to try to push, unless they were willing to open up questions on Ethereum's securities status more broadly, and it's likely that the call has come in somewhere to not take that fight," Edwards said.

Crypto markets took another leg higher last week, after data showing a slowdown in U.S. inflation drove a rally in risk assets.

(Reporting by Elizabeth Howcroft and Alun John; Editing by Amanda Cooper and Emelia Sithole-Matarise)