By City A.M. Reporter Steel giant Tata is to press ahead with plans to close blast furnaces at its biggest plant, threatening more than 3,000 jobs, according to sources. Unions were meeting the company on Thursday after presenting alternative proposals aimed at saving jobs in Port Talbot, south Wales. Sources said Tata rejected the plan and were pressing ahead with proposals for a greener form of steelmaking to cut emissions and stem financial losses. Unions will consult their members on how to respond to job losses, with industrial action not being ruled out. Sources said Tata accepted a unio…