US troop deployment 'threatens international peace': Zarif

"Increased US presence in our region is very dangerous and a threat to international peace and security and must be confronted," Zarif told the official IRNA news agency before heading home from a visit to Pakistan.

Zarif visited Pakistan to hold talks with his Pakistani counterpart, Shah Mehmood Quresh.

While meetings with Prime Minister Imran Khan were not made public, there has been speculation that Iran is looking to Islamabad and its close relationship with Riyadh to help de-escalate the situation in the Gulf.

His visit to Pakistan came after he and Iranian President Hassan Rouhani were both called out by Iran's Supreme leader for their "weakness". 

Ayatollah Ali Khamenei lambasted Zarif and Rouhani as failing to implement the leader's orders over Iran's 2015 nuclear deal with world powers.

Khamenei had claimed the deal had "numerous ambiguities and structural weaknesses" that could damage Iran.

Urging restraint

Ahead of Zarif's arrival, Pakistan's foreign ministry called on "all sides to show restraint, as any miscalculated move, can transmute into a large-scale conflict."

Washington says the reinforcements, which come after the deployment earlier this month of an aircraft carrier task force, B-52 bombers, an amphibious assault ship and a missile defence system, are in response to "campaign" of recent attacks approved by Iran's top leadership.

"Americans make such claims to justify their hostile policies and to create tension in the Persian Gulf," Zarif said.

The United States this month ended the last exemptions it had granted from sweeping unilateral sanctions it reimposed after abandoning a landmark 2015 nuclear between major powers and Iran in May last year.

The move dealt a heavy new blow to Iran's already reeling economy as even vocal critics of the renewed sanctions, like Turkey, announced they had stopped buying Iranian oil.