Feb 15 Nippon Steel & Sumitomo Metal Corp is willing to participate in a potential capital increase for ailing Brazilian steelmaker Usinas SiderAorgicas de Minas Gerais SA if an understanding with other shareholders is reached in principle, a source with direct knowledge of the matter said on Monday. The source, who requested anonymity because of the sensitivity of the issue, said that an accord between Nippon Steel and Techint Group - the other controlling shareholder at the steelmaker known as Usiminas, is unlikely to happen before the latter releases fourth-quarter results on Thursday.