NEW YORK (Reuters) - Fitch on Tuesday upgraded Latvia further into investment-grade status, citing the country's invitation to join the euro zone in the coming year.

The agency raised Latvia to BBB+ from BBB. The outlook is stable.

"Euro adoption will enhance economic policy coherence and credibility compared with the current exchange rate peg to the euro," Fitch said in a statement.

"The Latvian economy is closely integrated with the European Union through trade, investment and substantial ownership of its financial sector by Nordic parent banks."

Latvia is ready to become the 18th country using the euro from the start of next year, the European Commission announced last month.

Standard & Poor's rates the country BBB+ with a stable outlook. Moody's rates Latvia Baa2 with a positive outlook.