The Port Authority of New York and New Jersey offered this week to guarantee financing for both of developer Larry Silverstein’s office towers on Church Street at the World Trade Center site, which are expected to cost about $4.2 billion. But Silverstein would only receive up to $1.2 billion in financing for the second tower if he raised $625 million from lenders or investors, according to a letter the Port Authority sent Monday to the Bloomberg administration. Assembly Speaker Sheldon Silver said he does not think the proposal gets Silverstein and the Port Authority any closer to a deal. On Monday, Silverstein Properties served the Port Authority with a “notice of dispute,” triggering a 10-day period in which the two parties will meet to try to resolve disagreements over the World Trade Center redevelopment. If the dispute isn’t resolved, Joseph Daniels, president of the WTC’s 10th anniversary memorial, warned yesterday that the commemoration could be in danger.