NEW YORK (The Deal) -- Mobile phone company NII Holdings (NIHD) - Get Report announced Monday it has retained financial advisers to review a range of strategic options, including M&A transactions as well as a debt restructuring.

Advisers from UBS Investment Bank are helping the loss-making, debt-burdened company evaluate business partnerships and M&A for the entire company or specific business units, while Rothschild is advising on capital structure transactions such as debt restructuring or refinancing.

Reston, Va.-based NII, which provides wireless phone services in Latin America, saw its common stock and unsecured debt nosedive after the company warned on Feb. 28 that it is in danger of violating its debt covenants in 2014 and faces liquidity issues in 2015. The company operates under the Nextel brand in Brazil, Mexico, Argentina, and Chile.

Potential covenant violations aren't NII's only short-term concern. Bondholder Aurelius Capital Management sent a March 4 letter to the company that accused NII of making intercompany transfers that violate its bond indentures and also of making fraudulent transfers.

"While we wish these concerns to be promptly and suitably resolved, rest assured we have no desire to exacerbate NII's financial stress if that can be avoided," the New York hedge fund wrote in the letter. "We therefore invite a constructive dialog [sic], to include both principals and counsel, at the earliest opportunity."

Aurelius claimed to hold more than 25% of NII's 8.875% senior notes due 2019 and a "significant percentage" of its 10% notes due 2016. Wilmington Trust Co. is the indenture trustee for the 10% senior notes and the 8.875% senior notes.

The hedge fund has retained Lawrence Robbins and Donald Burke of Robbins Russell Englert Orseck Untereiner & Sauber to advise on the matter.

The letter, which was signed by Aurelius chairman Mark Brodsky, argued that three of the company's intercompany transactions violated its note indentures: a December 30, 2009, intercompany transfer of equity interests from NII Global Holdings Inc. to Nextel International Holdings Sarl; a release of note guarantees by McCaw International LLC, Airfone Holdings LLC and Nextel International (Uruguay) LLC that "purportedly" occurred on that same day "as a result of that illicit transfer"; and certain unspecified intercompany transactions related to a 2013 note issuance by NII International Telecom SCA.

Aurelius also asserted that NII committed fraudulent transfers relating to NII International Telecom SCA in 2013. An Aurelius spokesman declined to comment.

Standard & Poor's downgraded NII to CCC with a negative outlook from CCC+ on March 4, citing an expectation of continuing Ebitda losses and increased default risk over the next year. In addition to those concerns, S&P noted in the report, "we now believe there is higher risk of the company breaching financial maintenance covenants in its various bank and vendor facilities over the next year."

NII and Rothschild didn't respond to requests for comment. A UBS spokeswoman declined to comment.

NII's debt structure consists of $700 million in 7.875% senior unsecured notes due Aug. 15, 2019 (announced May 16, 2013); $900 million in 11.375% senior unsecured notes due Aug. 15, 2019 (announced Feb. 11, 2013); $1.4 billion in 7.625% senior unsecured notes due April 1, 2021 (announced March 24, 2011); $500 million in 8.875% senior unsecured notes due Dec. 15, 2019 (announced April 5, 2010); and $800 million in 10% senior unsecured notes due Aug. 15, 2016.