Israel has privately expressed concerns to the Trump administration about a new nuclear facility reportedly built in the Saudi desert with Chinese help, Israeli officials said.

Why it matters: This secret development raises concerns that the Saudis are building infrastructure for a future military nuclear program.

What's happening: Israeli defense and intelligence officials raised concerns with their U.S. counterparts after both The New York Times and The Wall Street Journal reported that the Saudis had teamed up with China to build a secret facility in the desert near Riyadh to produce yellowcake, a basic material for uranium enrichment.

What they're saying: A senior Israeli intelligence official said there are "worrying signs about what the Saudis might be doing, but it is not exactly clear to us what's going on in this facility."

• "The U.S. and the International Atomic Energy Agency (IAEA) also don’t have a clear picture about what’s going on there, and they are in the process of clarifying it with the Saudis," the official said.

Prime Minister Benjamin Netanyahu is treading carefully to avoid damaging relations with both Saudi Arabia and China, Israeli officials told me.

• Saudi Arabia is one of Israel’s main secret allies against Iran in the region, and Israel hopes the kingdom will follow the United Arab Emirates in normalizing relations with Israel.
• The Israeli intelligence community, as well as the foreign and defense ministries, are following the issue but were instructed by Netanyahu's office not to discuss it publicly.

Israeli officials think the Saudis decided to work with the Chinese on the new facility because the Chinese don't require assurances that nuclear technology will be used only for peaceful purposes.

• In contrast, the U.S. strictly conditions any nuclear cooperation with Saudi Arabia on such assurances.

Background: The production of yellowcake is a preliminary phase in the refinement of uranium. The Nuclear Nonproliferation Treaty does not compel the Saudis to update the IAEA about the existence of such a facility.