insert – Constraint in ON CONFLICT clause has no associated index

I have this simple setup

    CREATE TABLE stop (
      id INT UNIQUE,
      name TEXT,
      PRIMARY KEY(id)
    );

    CREATE TABLE line (
      id INT UNIQUE,
      name TEXT,
      PRIMARY KEY(id)
    );

    CREATE TABLE line_stops_sequence(
      id SERIAL PRIMARY KEY,
      line INT,
      stop INT,
      CONSTRAINT fk_line FOREIGN KEY(line) REFERENCES line(id),
      CONSTRAINT fk_stop FOREIGN KEY(stop) REFERENCES stop(id)
    );

When I launch the following sentence

INSERT INTO line(id, name) VALUES (1, 'Line 1');
INSERT INTO stop(id, name) VALUES (2, 'Stop 2');
INSERT INTO line_stops_sequence(line, stop) VALUES (1,1), (1,2) ON CONFLICT ON CONSTRAINT fk_stop DO NOTHING;

I get constraint in ON CONFLICT clause has no associated index;

I know I’m inserting an stop id that is not included in the stop table. The idea is that I want to ignore the INSERTs that have conflicts. In the example it is just two items, but I’m inserting bulk data.

How can I do it without having to manually check the result of the query? Is there anyway to do it with the SQL sentence?