By Ian Chua

SYDNEY (Reuters) - Singapore will fund a A$2.25 billion (US$1.7 billion) expansion of military training facilities in Australia in a deal due to be announced on Friday, according to a government source.

Land-scarce Singapore has long sent troops to Australia for military exercises. The new deal would allow the Asian nation to increase the number of troops it has on rotation in Australia to 14,000, from 6,000.

Under the agreement, Singapore would fund the cost of expanding the Shoalwater Bay Training Area and the Townsville Field Training Area, both in the north of Queensland state.

Both bases lie in electorates critical to the government. The timing of the expected announcement by Prime Minister Malcolm Turnbull is viewed as a political coup ahead of an anticipated July federal election.

The move to forge closer military ties between Australia and Singapore comes at a time of rising tensions between much of Asia and China, which has been building military and civilian facilities on its artificial islands in the disputed South China Sea.

($1 = A$1.3396)

(Reporting by Ian Chua; Editing by Jane Wardell, Toni Reinhold)