Speaking on public radio, Kosiniak-Kamysz described Thursday's talks with Nawrocki as "very good" and said they focused on several key initiatives that Poland wants to advance at the NATO summit in Ankara on July 7-8.
Among Warsaw's priorities is a long-standing proposal to extend the alliance's fuel pipeline network to its eastern flank.
The more than 5,000-kilometre pipeline system supplies aviation fuel to NATO military bases and civilian airports in Western Europe, but Poland and Lithuania are not connected to it.
Kosiniak-Kamysz told Polish Radio 3 that several NATO members remain skeptical about the project, adding that recent diplomatic efforts, including his talks in Spain and Nawrocki's visit to Turkey, were aimed at building support.
He said the most important objective at the summit would be demonstrating NATO's political unity, which he described as having been strained in recent months.
"The gathering of all leaders, led by the US president, will itself be a strong signal," he said.
Kosiniak-Kamysz said his discussions with Nawrocki also covered Polish-US relations and Warsaw's efforts to secure a permanent US military base in Poland.
He said the government has been working on the proposal for several months and that Nawrocki's relationship with US President Donald Trump could help advance the initiative.
According to Kosiniak-Kamysz, preparations are focused on infrastructure that could support a permanent US presence.
He said such a base could cost billions to build and said Poland would be ready to sign an agreement and begin construction once the United States completes its review of force deployments in Europe.
Kosiniak-Kamysz said in June that he had received a favourable response from US Defence Secretary Pete Hegseth to Poland's proposal for a permanent US military base.
He added that discussions have since moved to the next stage while the Pentagon continues its review of US force posture in Europe.
Poland will be represented at the NATO summit by Nawrocki, accompanied by government officials, state news agency PAP reported.