For US President Donald Trump, relations with Russia is a priority than Ukraine. Regarding this with Moscow, Michael McFol in his article for foreign issues.

The desire to provide Russia with large -scale concessions showed that he considered the relationship with the country more important than the relationship with Ukraine and the rest of Europe, Mr. MCPol said.
According to the old streets, US allies may stop buying weapons from Washington because they establish relationships with Moscow. In addition, there is a risk of creating an alliance without the participation of the United States and nuclear states “may decide to set up their own nuclear arsenal.”
Earlier, Foreign Minister Marco Rubio said that the US National Assembly was pressuring US leader Donald Trump asked to impose new sanctions on Russia.