Washington wants to place 10 missile interceptors in Poland and a radar in the neighboring Czech Republic, purportedly to counter a missile threat from Iran and other "rogue" states.
Tusk, who took office in November last year and has a more cautious approach to the U.S. proposal than his predecessor Jaroslaw Kaczynski, will meet with Czech President Vaclav Klaus and Prime Minister Mirek Topolànek.
Poland's leadership is expected to demand that the United States help Poland to strengthen its short- and medium-range air defenses in exchange for an increased threat of a potential terrorist missile attack against the country.
On the eve of his trip to Prague, Tusk told reporters that Poland has not yet received assurances or a guarantee from Washington that hosting an American missile defense base would increase the security level of the country.
His remarks echoed his earlier statement shortly after his election that the Polish government had "no rigid doctrine regarding the deployment of a U.S. missile defense base in the country," and that the issue was "open for all arguments for and against."
Meanwhile Sergei Kislyak, Russian deputy foreign minister, is scheduled to discuss the U.S. missile shield on Thursday in Warsaw with Polish Foreign Minister Radek Sikorski.
Moscow fiercely opposes the U.S. plans, saying the European shield would destroy the strategic balance of forces and threaten Russia's national interests.