ROME (Reuters) – Monte dei Paschi di Siena will be able to sign by Tuesday a contract with a group of banks which are due to underwrite its up to 2.5 billion euro ($2.4 billion) new share issue, a source with knowledge of the matter said. The bank has called a board meeting on Tuesday to approve the terms of the rights issue, another source previously said, and needs to have a guarantee contract signed with banks by then. ($1 = 1.0321 euros) (Reporting by Giuseppe Fonte, writing by Valentina Za; editing by Agnieszka Flak)