Sikorski is demanding security guarantees from the United States as part of a deal to install 10 interceptors in Poland at talks in the U.S. this week.
The U.S. plans to deploy elements of its missile defense shield in Poland and the Czech Republic citing a threat from Iran. Russia has fiercely opposed the plans threatening to retarget nuclear missiles at the two countries.
Sikorsky said he is satisfied that the principles on which Poland have insisted on have been accepted, but the negotiations will continue. He added the two countries' experts have a lot more to do.
The minister said Poland is seeking to strengthen its missile defenses and thereby expand its capabilities as a U.S. ally in Europe.
U.S. Secretary of State Condoleezza Rice said after the talks the Bush administration backs Warsaw's request for aid in modernizing its missile defenses.
In Washington, Sikorski is still to meet with Vice President Dick Cheney, and the president's national security adviser Stephen Hadley.
Poland's new government, which came to power in November, has taken a more cautious approach to the U.S. proposal than former Prime Minister Jaroslaw Kaczynski's cabinet, which supported the plan.