Liverpool has been beset by injuries to their backline, with Virgil van Dijk, Joe Gomez and Joel Matip all sidelined. Such has been the Reds need that midfielder Jordan Henderson has been forced to deputize in the center of Liverpool's defense. Long would provide a short-term depth option to alleviate the Reds' shortage of backline options.
Manager Jurgen Klopp made it clear after Liverpool's 3-1 victory at Tottenham Hotspur that he would be keen to add a new central defender in this month's transfer window.
"If you have a center-half available at a reasonable price, and one with the quality we need, then send me a message," he said on BT Sport.
"We thought [about making signings] and we think the whole time but it's about doing the right thing. We need to find the right player. It's incredible what's happening in the defensive line."
Liverpool did not officially confirm interest in the defender when approached by ESPN for comment.
The link with Long comes amid increasing European interest for the USMNT international defender. The Washington Post reported that English Championship side Reading want to bring Long in on loan, while MLSSoccer.com said there was "interest from clubs in England and France."
A league source told ESPN on Thursday that the Red Bulls had yet to receive any formal offers for Long. The transfer window in Europe closes Monday night.
Long, 28, is something of a late bloomer. He was drafted by the Portland Timbers in 2014, but was released in midseason having had loan stints in the USL Championship with Sacramento Republic and the Orange County Blues.
He soon latched on with the Seattle Sounders and spent 2015 playing for their reserve team. In 2016 Long went on trial with the Red Bulls and was signed to their reserve team, New York Red Bulls II, and spent the entire 2016 season in the USL.
In 2017, Long made a breakthrough into the Red Bulls first team, and has been a mainstay ever since, making 120 league, cup and playoff appearances, scoring nine goals. He was named MLS Defender of the Year in 2018, a season in which the Red Bulls claimed the Supporters Shield, which goes to the team with the highest regular season points total.
Long's form then caught the eye of U.S. men's national team manager Gregg Berhalter, with Long making 18 appearances for the U.S. while scoring three goals. Long is in training camp with the U.S. side, and is expected to suit up in a friendly against Trinidad & Tobago this Sunday in Orlando.