WARSAW, Sept 27 (Reuters) - U.S. weapons maker Raytheon has signed a letter of intent with Polish military software producer WB Electronics to cooperate in bidding for a contract to build Poland's planned anti-missile system, Polish state radio said on its website.

Under the agreement, WB Electronics is to provide software for training and tactic simulations for the system, dubbed "Shield of Poland". The two companies would also cooperate in seeking export opportunities.

WB was not immediately available for comment.

Raytheon, which offers the Patriot missile defence system, is in the running to build Shield of Poland, competing with a consortium of Franco-Italian missile maker MBDA and France's Thales.

The cost of the project is estimated at 26 billion zlotys ($7.9 billion). Fifteen years after its admission to NATO, Poland is stepping up military investments, particularly in light of the latest standoff between Ukraine and Russia.

Eastern Europe's largest economy wants to raise its defence spending to 2 percent of gross domestic product (GDP) from 2016. (1 US dollar = 3.2955 Polish zloty) (Reporting by Adrian Krajewski; Editing by David Holmes)