The pact is "top of our list," said the official, who spoke on condition of not being identified.

Few details were provided about what the declaration would include, but the official told reporters it would underline "the importance of the United States and Poland having a common approach to 5G."

The United States is pressing allies, with mixed success, to reject Chinese 5G technology, especially from the giant mobile phone company Huawei.

Washington fears that Huawei will provide Beijing with a way to spy on communications from the countries that use its products and services.

"The United States and some of its strongest allies, including Poland, are working" on a joint strategy, including a focus on ensuring "supply chain security," the official said.

Pence is traveling to Poland to attend ceremonies marking the 80th anniversary of the start of World War II. President Donald Trump had been due to attend but canceled on Thursday, sending Pence instead, so that he could monitor the approaching Hurricane Dorian.

Polish President Andrzej Duda has pushed hard for tight links to Trump's White House, and the official said the administration is "grateful for the incredible support we've had from this important ally."