Hina received the letter dated November 13 on Friday. The senators, led by Republican George Voinovich from Ohio, also underlined Croatia's progress in democracy and integration with Euro-Atlantic institutions and standards.
The senators said Croatia should be invited to join NATO together with the other candidates which were ready for membership.
They recalled that Croatia was part of the Membership Action Plan since 2002, that it had successfully completed four MAP rounds, that the government had launched a long term strategy to restructure the armed forces, and that it was committed to meeting all the terms for NATO integration.
The senators underlined Croatia's engagement in promoting NATO's values and strengthening security with other countries, for example by participating in the ISAF mission in Afghanistan, providing training programmes in Iraq and supporting the global war on terror.
Croatia is actively participating in the initiative to prevent the proliferation of weapons of mass destruction, and is showing its leadership in the war on terrorism by chairing the South East European Cooperation Process and the Task Force of the region's defence ministers against proliferation and terrorism and for border control, said the letter.
The senators recalled the Senate's Resolution 342 from December 2005, which recommended the admission of Croatia to NATO. They said Croatia's place was in NATO and voiced hope the Riga summit would send a message to Croatia and other candidate countries with a clear statement about the time of the next enlargement round.
After a meeting with Croatian Prime Minister Ivo Sanader at the White House last month, President Bush said he would push in Riga for Croatia's accession to NATO in 2008.