Reuters) - A number of members of the US Congress expressed concern over the fallout of Defense Secretary James Matisse 's resignation and saw the move as an indication of the worsening crisis in the country's administration. 

Republican Senator Marco Rubio warned that Matisse's resignation letter to President Donald Trump showed the White House was pursuing a foreign policy that could have serious consequences. 

"Read General Mattis's letter of resignation. It is quite clear that we are heading towards a series of grave political mistakes that will endanger our nation, damage our alliances and strengthen our enemies," the senator wrote on Twitter.

"We, who have supported the initiatives of this administration over the past two years, are able to convince the president to choose a different approach," Rubio said. 

For his part, Democratic Senator Mark Warner in a tweet to him the departure of Matisse "scary" and described the defense minister as "an island of stability amid the chaos in the Trump administration." 

"What we saw through the president's indiscriminate approach toward Syria underscores that our national defense is so important that it can not be subject to the volatile whims of the president," he said. 

Democratic leader Nancy Pelosi told reporters yesterday that she was "shocked by the news of Matisse's resignation, which she described as patriotic. 

" "Our forces are looking at General Matisse as a leader, and now he will leave them.This is very dangerous for our country. "

According to Pelosi, Matisse was "a calm for many of us, and the voice of stability in the Trump administration." 

"Look just this week, when the president withdraws his troops from Syria without full consultation already with the national security leaders in his administration, and he has changed his position on signing the government financing bill," the Democratic leader said. 

Matisse sent a letter to Trump on Thursday, in which he resigned, explaining his decision to have substantial differences with the president on the administration of the country's policy.