Washington DC: Defence Secretary James Mattis, who batted for strong Indo-US military ties, has resigned, citing irreconcilable policy differences with Donald Trump after the US President shocked the Pentagon by deciding to withdraw American troops from strife-torn Syria.
Mattis, latest in a string of senior US officials to quit the Trump administration, in a letter to the president said that he should choose a person who is more in tune with his world view.
Trump announced the resignation in two tweets on Thursday evening, and said Mattis, will leave at the end of February.
According to reports, 68-year-old Mattis, a retired United States Marine Corps General, went to the White House on Thursday afternoon in a last attempt to convince Trump to keep US troops in Syria. He was rebuffed, and told the president that he was resigning as a result.
Separately on Thursday, there were reports the White House was also planning a sharp cut to troop numbers in Afghanistan.
In his extraordinary resignation letter, Mattis told Trump he had "the right to have a Secretary of Defence whose views are better aligned with yours".
Mattis' resignation letter, a Pentagon spokeswoman said was hand-delivered to the president. In the letter, Mattis told Trump it was the "right time" for him to step down.
"The end date for my tenure is February 28, 2019, a date that should allow sufficient time for a successor to be nominated and confirmed as well as to make sure the Department's interests are properly articulated and protected at upcoming events to include Congressional posture hearings and the NATO Defense Ministerial meeting in February," Mattis said.
The Pentagon chief did not mention if he was resigning specifically over the troop withdrawal decision, which has surprised US allies and even Republican lawmakers.
Mattis was a great advocate of strong Indo-US defence relationship and New Delhi's growing role in the strategic Indo-Pacific amidst China flexing its muscles in the region.
Earlier this month, Mattis hosted Defence Minister Nirmala Sitharaman at the Pentagon for talks on India-US defence relationship.
"The US-India relationship is a natural partnership between the world's oldest and the world's largest democracy," Mattis had said then.
He visited India in September for the inaugural India-US 2+2 Dialogue. In April this year, Mattis appealed to Congress to urgently provide India the national security waiver, saying imposing sanctions on it for buying the S-400 air defence missile system from Russia would only hit the US.
Analysts say the withdrawal of troops will please US enemies by clearing the way for Syria's Bashar al-Assad regime, Russia and Iran. Mattis had warned that removing ground forces from the Middle Eastern country would be a "strategic blunder". Currently, there are about 2,000 US forces in Syria.