"North Korea has been engaged in a pattern of provocative behaviour", McMaster said. It will distract from coverage of the summit in USA media.
However, the talks produced progress in Trump's efforts to reduce the trade deficit with the world's No. 2 economy.
Tillerson said Trump accepted Xi's invitation to visit China.
Trump has previously threatened unilateral action against the reclusive state, a threat that appeared more palpable after Thursday's strike on a Syrian airfield following an apparent chemical attack.
Iran, which also backs Assad, denounced the USA strike, saying it was "dangerous, destructive and a violation of worldwide laws" to use chemical weapons as an excuse for unilateral action. Russia, which has military forces in Syria aiding Assad's government, says the deaths were caused by a gas leak from a depot where rebel groups stored chemical weapons, a charge the rebels deny and USA intelligence officials say is false. The highly anticipated U.S.
White House press secretary Sean Spicer said the attack "sends a very strong signal not just to Syria but throughout the world".
He said Taiwan should pay attention to a possible visit by Trump to China later this year and the development of U.S. The strike group, which includes an aircraft carrier, will make its way from Singapore toward the peninsula, a USA official told Reuters on Saturday. "And I think even China is beginning to recognize that this presents a threat to even - to- to China's interests as well".
EPL leader Chelsea loses 2-1 to Crystal Palace
Palace and Chelsea are likely to face Football Association scrutiny after pyrotechnics were set off during the match. Defenders James Tomkins (calf) and his replacement Scott Dann (knee) went off injured.
Xi and Trump also discussed China's increased militarization in the South China Sea, with President Trump urging the Chinese to adhere to global norms.
Trump said Friday that he and Xi made "tremendous progress" in their talks and that he believes "lots of very potentially bad problems will be going away".
On defence ties, which he said make up an important part of the bilateral relations, Xi pointed out that mutual trust in military and security areas forms the basis of the strategic mutual trust between the two countries.
If the Xi administration does not want a disturbance to erupt on the Korean Peninsula, it needs to restrict the supply of oil and other assistance to North Korea while also stemming that country's military provocations, such as a nuclear test and a ballistic missile launch.
"China has a great influence over North Korea", Trump said.
The US president has said that if China doesn't exert more pressure on North Korea, the US will act alone.
The US naval move will certainly raise tensions in the region and comes hard on the heels of a US cruise missile strike on Syria that was widely interpreted as putting Pyongyang on warning over its refusal to abandon its nuclear ambitions.
Anchor: U.S. Secretary of State Rex Tillerson says China has agreed that North Korea's nuclear threat is at a stage that calls for action.