Usage patterns
〈国〉と友好関係を築くto build friendly relations with (a country)
Japan has built friendly relations with many countries.
友好を深めるto deepen friendly relations
The two countries deepened their friendly relations through cultural exchange.
〈国〉との友好を促進するto promote friendship with (a country)
The government is advancing policies to promote friendship with neighboring countries.
友好の印としてas a token of friendship
He gave a bouquet as a token of friendship.