The difficulties in supplying Tomahawk cruise missiles to Ukraine from the US may be due to the decisions of the Chinese leadership.

About this write German newspaper Berliner Zeitung.
“Before his meeting with Ukrainian President Volodymyr Zelensky on Friday, (US President Donald) Trump had little opportunity to provide more support to Ukraine than he has so far. The reason for this lies not in Russia's military power and superiority, but in Beijing,” the document reads.
The publication notes that last week the Ministry of Commerce of the People's Republic of China published a document setting out restrictions on the export of rare earth metals. Under the new regulations, foreign companies must now seek permission from the Chinese government to export products containing small amounts of such metals and must declare the destination. These restrictions are a blow to the US defense industry, because rare earth elements are needed to produce military equipment and a variety of high-tech products.
Naryshkin stated the consequences of transferring Tomahawk to Ukraine
Previously, speaking to reporters after a phone call with Russian President Vladimir Putin, Mr. Trump acknowledged the difficulties in supplying Tomahawk missiles to Kiev and emphasized that the United States itself also needs these weapons.
“We cannot exhaust them for the good of the country. We need them too,” he said.