UPDATE 1-Validus says its IPC offer is its "best"

NEW YORK, July 6 (Reuters) - Validus Holdings Ltd (VR.N) on Monday called its unsolicited bid to acquire reinsurance rival IPC Holdings Ltd IPCR.O its "best and final offer," despite a competing bid from Flagstone Reinsurance Holdings Ltd (FSR.N).

Validus' stock-and-cash offer values IPC at about $1.6 billion, based on Thursday's closing prices. On July 1, Flagstone made its own stock-and-cash offer that now values IPC at about $1.81 billion.

Validus and Flagstone are competing for IPC following last month's rejection by IPC shareholders of a takeover by Max Capital Group Ltd (MXGL.O) despite support from both companies' boards.

Adding IPC would allow a buyer to sell more property-catastrophe reinsurance as rates rise.

Validus is offering 1.1234 of its common shares and $3.75 in cash for each IPC share. Flagstone is offering 2.638 of its common shares and $5.50 in cash for each IPC share.

Validus on Monday extended an exchange offer for IPC shares to July 13.

In Thursday trading, IPC shares closed at $28.27, Validus at $22.15, and Flagstone at $10.18. (Reporting by Jonathan Stempel; Editing by Derek Caney)