Swansea City's Liberty Stadium could be expanded as part of the takeover plans. Michael Steele/Getty Images

Swansea City are the subject of an advanced takeover bid by American duo Steve Kaplan and Jason Levien, the club confirmed on Saturday.

Kaplan, the co-founder of Oaktree Capital Group and vice chairman of the NBA's Memphis Grizzlies, and D.C. United managing general partner Levien are finalising an agreement to purchase a controlling interest in the club.

Sources told ESPN.com that Kaplan and Levien, who partnered in Memphis when Levien served as the Grizzlies' CEO, have built a strong relationship with longtime Swansea chairman Huw Jenkins, as well as the club's board of directors and leaders in their supporters' trust.

The pair are nearing completion on a deal that would give their investment group a majority share in the club while keeping the well-regarded Jenkins in place as CEO and their co-chairman.

"Talks will continue with the aim of an agreement being ratified by the end of the season," said a club statement.

Under Jenkins' guidance, Swansea are in the midst of the most successful five-year run in the history of the Welsh club, starting with an 11th-place finish in 2011-12 in the Swans' first season in the Premier League.

Swansea followed that promising debut with finishes of ninth, 12th and eighth -- including a historic League Cup triumph in 2013 -- and have risen to 13th in the current table after a slow start this season.

A 1-0 home win over Chelsea on Saturday has moved Swansea past the traditional 40-point mark synonymous with Premier League safety, with a comfortable 13-point cushion above the relegation places with five games to go this season.

Gylfi Sigurdsson scored Swansea's winner against Chelsea on Saturday. GEOFF CADDICK/AFP/Getty Images

Sources say Kaplan and Levien are interested in expanding Swansea's current 20,520-seat stadium, investing in the club's player and academy budget and growing their brand internationally.

"We believe we have a proposal which will help Swansea City progress both on and off the field," Jenkins said.

Recent reports have claimed Swansea have an interest in bringing back former Swans manager Brendan Rodgers next season, who is a free agent after being sacking by Liverpool in October. They are currently managed by Italian coach Francesco Guidolin.

If the proposed Swansea deal is finalised as expected, D.C. United would become the third Major League Soccer franchise to share common ownership with a Premier League team, joining New York City FC (Manchester City) and the Colorado Rapids (Arsenal).

The plan, sources say, is for D.C. United and Swansea to work closely together on both the football side and the business side, with Levien's experience in stadium projects seen as a significant boost for Swansea in their planned expansion of the Liberty Stadium.

Levien is in his fifth season as the managing general partner for D.C. United and is widely credited for spearheading the drive behind the long-awaited construction of a soccer-specific stadium in the nation's capital after a two-decade wait. The new stadium is scheduled to open in time for the start of the 2018 MLS season.

Levien largely assembled the Robert Pera-led ownership group which took over the Grizzlies in June 2012. In the next season, Memphis advanced to the conference finals for the first time in franchise history and placed No. 1 in ESPN The Magazine's 2013 Ultimate Standings survey.

Levien also serves as a key adviser to Inter Milan majority owner and president Erick Thohir, who purchased the Italian giants in 2013. Thohir and fellow Indonesian billionaire Handy Soetedjo are partners at Inter Milan as well as co-owner of D.C. United with Levien.

Swanser's Supporters Trust -- which owns 21 percent of the club and have a representative on the board -- published an article on its website on Tuesday saying it was "open-minded" over the issue of a change in the shareholding of the club.

Representatives of the Trust met with Levien on Saturday morning, ahead of Swansea's 1-0 home victory over Chelsea, and the meeting was described as "constructive".

But the Trust statement added: "It would be highly premature for us to reach any conclusion on whether such a sale on the terms proposed would be in the best interest of the football club and its supporters."

The Trust also added it was disappointed that it was not provided with more time to consider the deal prior to it being made public.

Trust chairman Phil Sumbler said: "We have been aware of the terms of the potential deal for around two weeks. It has become apparent though that the discussions have been taking place since December and not all shareholders have been allowed to be part of those discussions.

"As we understood from two meetings I attended this morning we are not near the conclusion that this announcement suggests, and we are surprised that the information was released without the consent of all shareholders."

Information from Press Association was used in this report.