The International Institute for Strategic Studies said Tehran has established a regional network of some 200,000 fighters.
Iran is widely expected to make extensive use of its special operation forces and regional proxy militias in a hypothetical future war with the U.S.
"We're in trouble," Steve Schmidt said in a Monday interview. "You see America in retreat, literally."
Trump is dismantling a U.S.-led global architecture built by four generations, paid for by thousands of American lives and trillions of dollars of investment.
Sources close to the Turkish leader told BBC News that Erdogan "thoroughly rejected" the letter dated last Wednesday and chucked it in the trash.
Senior 2020 campaign adviser Lara Trump said average Americans had to "Google" who the Kurds of northern Syria even are before they could be outraged about President Donald Trump's decision to withdraw troops from the region.
"I am absolutely appalled that the United States is going to betray those Democratic forces in northern Syria," Pat Robertson said on "The 700 Club."
"By abandoning the Kurds we have sent the most dangerous signal possible – America is an unreliable ally," the Republican senator from South Carolina argued.
Between 19 and 21 people have been killed and hundreds injured as protesters clash with Iraqi security forces over calls for more job opportunities, an end to corruption and better access to social services.
Saudi Arabia has denied Iran's claims of receiving official messages from the kingdom, but once again, Iraq sought to play a role in mediating the Middle Eastern feud.
Iraq and Syria have boosted relations despite the U.S. opposing the latter's government and attempting to curb the influence of their mutual ally Iran.
"Our region is on the edge of collapse, as a single blunder can fuel a big fire," Rouhani warned fellow Middle East leaders.
Iranian President Hassan Rouhani invited Saudi Arabia and other nations in the Persian Gulf to join a "Coalition for Hope" but Saudi State Foreign Affairs Minister Adel al-Jubeir skipped the speech.
U.S. officials "appreciate the work of the UN Secretary General, UN Envoy Pedersen, Turkey, Russia, and the members of the Small Group in achieving this result," but made no mention of Iran's role.
Iran's upcoming "Hormuz Peace Endeavor" would include an invitation for potential cooperation with Saudi Arabia as a gesture to work together in the world's most important maritime oil chokepoint.
Iranian parliament speaker Ali Larijani also labeled an American-led coalition currently stationed to protect commercial interests in the area "a new means for plundering the region."
"If the Americans think of any conspiracy, we will respond from the Mediterranean to the Red Sea to the Indian Ocean," a top Iranian military official said.
Secretary of State Mike Pompeo told reporters "it was Iran" that attacked Saudi Arabia over the weekend, breaking with the Pentagon, which said it was "not going to get ahead of the Saudi investigation."
Experts tell Newsweek why Japan hasn't signed on to a U.S.-led military buildup against Iran in the Persian Gulf and why Tokyo remains a potential player for peace between Washington and Tehran.
Saudi Arabia and Yemen's Houthi rebel movement held rival press conferences as Iran continued to deny any involvement in attacks on the kingdom's oil sites.
"The Americans need hotbeds of tension in Syria only to justify their illegal presence on the territory of a sovereign state and to satisfy their geopolitical ambitions by any means," a senior Russian military official said.
The U.S. has yet to provide evidence to back up claims it was Iran, not Yemen's Houthi movement that was behind an attack on Saudi Arabia's oil facilities.
Russian President Vladimir Putin advised Saudi Arabia to make the same "wise state decision" as Iran and Turkey in buying his country's advanced missile defenses.
President Donald Trump argued that Iran lied about its June attack on a U.S. drone and may also be untruthful about a recent attack against Saudi oil sites.
Yemen's Iran-backed Houthi rebels claimed responsibility for drone attacks at the world's largest oil processing facility in Saudi Arabia, military and government spokespersons said Saturday.
"It is great news for America," the right-wing host said of Trump's national security advisor's ouster.
"We love Jason, so he's always additive to the team," Trump said of Middle East envoy Jason Greenblatt's resignation. "But the plan's in a great place."
Russia has expressed support for the sovereignty of Iraq, Syria and Lebanon following attacks attributed to Israel against regional partners of Iran.
The head of Iran's aerospace sector said that "the Russians and the Chinese have given us proposals" for fighter jets about a year before a U.N. arms embargo is set to expire.
"I'm not sure I'm ready to call the crisis over yet, but so far so good," Defense Secretary Mark Esper said.