BBC:

By Amir Azimi

The continued build-up of US military in the Gulf region now points less to signalling and more to preparation.

The arrival of the USS Abraham Lincoln carrier strike group near Iranian waters is already a significant move.

Another aircraft carrier, the USS Gerald R Ford, was last seen near the Strait of Gibraltar and has been heading east to support potential operations. Other assets have also been moved to the region, reinforcing the impression that Washington is assembling layered military options.

Such deployments can serve as leverage in diplomacy. But taken together, they may also suggest that indirect talks between Tehran and Washington have reached a deadlock - one that could be followed by military action if neither side shifts positions.

This raises a fundamental question: why do Iranian leaders, at least publicly, remain defiant in the face of the world's most powerful military and its strongest regional ally in the Middle East?

The answer lies in Washington's stated conditions for talks.

US condition seen as capitulation

From Tehran's perspective, these demands amount not to negotiation but to capitulation.

They include ending uranium enrichment, reducing the range of ballistic missiles so they no longer threaten Israel, halting support for armed groups across the region, and, as US Secretary of State Marco Rubio has stated, changing the Islamic Republic's treatment of its own citizens.

For the Iranian leadership, these are not secondary policies. They form the core of what it sees as its security architecture.

In the absence of powerful international allies, Tehran has spent decades building what it calls the "Axis of Resistance".

It is a network of allied armed groups designed to keep confrontation away from Iran's borders and shift pressure closer to Israel.

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