WARSAW (Reuters) - Poland will almost certainly sign a bilateral security agreement with Ukraine before July's NATO summit in Washington, the Polish prime minister said on Friday.

On Thursday, Prime Minister Donald Tusk said that before the NATO summit in Washington, which starts on July 9, talks will be held in Warsaw with the president of Ukraine.

"I must, together with the defence minister, determine how we can continue to help Ukraine, but we cannot weaken Poland's defence capabilities," Tusk told reporters.

"There is a 99% chance that we will sign this agreement with President Zelenskiy (before the summit)."

Tusk said that the agreement was practically "finished" and only a few details and wordings needed to be clarified.

The European Union and two of its member countries, Lithuania and Estonia, signed security agreements with Ukrainian President Volodymyr Zelenskiy at a summit in Brussels on Thursday.

(Reporting by Alan Charlish, Pawel Florkiewicz; editing by Miral Fahmy)