The phrase "a friendly nation" is correct and usable in written English.
You can use it to describe a country that has amicable relations with another country or is generally perceived as supportive and cooperative.
Example: "During the summit, leaders from a friendly nation expressed their willingness to collaborate on various international issues."
Alternatives: "an amicable country" or "a supportive nation".
Russia is not a friendly nation to the United States.
We must consider whether refugees fleeing the persecution of their home country may be better served by resettlement in a friendly nation closer to their homes.
"There are much bigger questions to be answered in relation to how Russia operates in the United Kingdom and whether they really are a friendly nation towards us".
The 41-count indictment unsealed today charges the 11 suspects with conspiracy, firearms violations and commencing an expedition against a friendly nation -- in this case, India.
But because he is accused of being a member of Al Qaeda, and is a citizen of a friendly nation, he should not be treated as a warrior.
Second, the failure of western democracies to respond to the dismemberment of a friendly nation, albeit a small one, can have very serious global consequences.
"I also told them… that it is unacceptable that a friendly country spies on other friendly nations," she told a press conference.
The United States has a choice: receive oil from a stable, friendly nation in Canada or get oil from volatile, unfriendly regimes overseas.
Its effects will be entirely negative – not just on the rights of gay men and women in Malawi, and elsewhere in Africa, but on the reputation of a usually friendly nation which likes to see itself as "the warm heart of Africa".
Ankara is more than just a nominally friendly nation.
In 1999, Olins's old company, Wolff Olins, proposed that Germany, the land of beer, Hitler and lederhosen, could be transformed in the eyes of the world into a warm and friendly nation "by replacing black in the current national colors with the European blue".
