The United States welcomed Tuesday former Cuban leader Fidel Castro's belated response to the thaw in ties between the Cold War foes as a sign that change is under way in Havana.
"We take his reference of 'international norms and principles' as a positive sign," state department spokeswoman Jen Psaki told reporters, after Castro's letter was released.
Psaki said Washington now looked forward "to the Cuban government implementing those international norms and principles for a democratic, prosperous and stable Cuba."
Last week, the highest-ranking US delegation in 35 years began negotiating with Cuban officials in Havana on restoring diplomatic ties, reopening embassies in their respective capitals and lifting some travel restrictions.
Psaki stressed though that there was "a lot more work to be done" and revealed the US has "invited Cuban officials to Washington in the coming weeks" to continue the talks.
No definite date has been set yet.
Fidel Castro, 88, and still an influential former leader of the Caribbean country released his letter to state media late Monday, after last week's historic first round of talks.
The revolutionary icon noted that he did not trust the United States, but did not repudiate the reconciliation process and defended the peaceful resolution of conflicts with "political adversaries."
And his language contained a nod to a normalization in ties.
"Any peaceful and negotiated solution to problems between the United States and the peoples or any people of Latin America, which does not imply force or the use of force, should be treated according to international norms and principles," Castro said.
Psaki countered however that it was not about trust.
It was "about what's in the interest of the people of Cuba, what's in the interest of our own national security interest, our economic interest," she said.
In December, US President Barack Obama and Raul Castro, who succeeded an Fidel as Cuba's president in 2006, agreed to begin normalizing ties more than 50 years after they were broken.