"Yes and yes: they will apply and they will be granted membership," a senior diplomat, who wished to remain anonymous, told the news agency.
According to the sources, during the ratification of the two countries' membership, which will take one year, NATO will increase troop presence in northern Europe and hold more military exercises.
The diplomats and officials in the alliance said membership bids by Sweden and Finland are to be approved either at a planned NATO summit, due in Madrid on June 28-30, or before it.
A NATO official said: "There's no exact timeline. We will not wait for the Madrid summit if it can be approved sooner."