Chinese President Xi Jinping flew into Moscow on Monday. He was expected to press Beijing's role as a potential peacemaker in the Ukraine conflict while Russian President Vladimir Putin hoped for support against Western pressure.
Xi is the only national leader to oppose the International Criminal Court's (ICC) arrest warrant for Putin.
Moscow said the charge was among a number of "clearly hostile displays" and Beijing said it reflects double standards.
Russia is presenting Xi's trip, his first since securing an unprecedented third term this month, as evidence that it has a powerful friend prepared to stand with it against a hostile West that it accuses of trying to isolate and defeat Moscow.
Xi arrived in Moscow on Monday afternoon and was due to hold "informal" talks with Putin, followed by dinner.
Formal talks are scheduled for Tuesday.
An arrest warrant for Putin was issued on Friday, citing Putin's deportation of Ukrainian children to Russia.