Dollar Falters as Iran Sanctions, Treasury Buybacks Compete for Market Focus

The U.S. dollar spent Tuesday morning in a holding pattern, unable to build on the gains it had scraped together overnight. In Hong Kong and across Asian trading floors, the currency was caught between two competing forces: the threat of new American sanctions on Iran, which typically strengthens the dollar as countries rush to secure access to it, and the Treasury Department's effort to buy back longer-dated bonds and bring down borrowing costs, which can weigh on the currency's appeal.

Treasury Secretary Scott Bessent had announced the Iran sanctions expansion on Monday, coupling it with a stark warning to other nations. Cut your business ties to Iran, he said, or face expulsion from the dollar-based financial system. The message was clear enough that some currency strategists saw it as a potential prop for the dollar. Ray Attrill, head of foreign exchange strategy at National Australia Bank, noted the logic: if countries feared losing dollar access, they might buy dollars preemptively before any restrictions took hold. That reasoning had helped lift the dollar index overnight, pushing it up 0.16% from three-month lows. But by Tuesday's Asian session, the momentum had stalled. The dollar index, which tracks the currency against six major peers, was down marginally at 98.96, suggesting the initial bounce had run out of steam.

Meanwhile, the Treasury was pursuing a different strategy to manage the bond market. After Bessent surprised investors the previous week by announcing a doubling of quarterly buybacks for longer-dated bonds—a move aimed at easing borrowing costs that had climbed to near two-decade highs—reports emerged that the Treasury might dip into its cash reserves to accelerate those purchases. The idea was to take pressure off yields that had been climbing steadily. Yet the relief was proving limited. The two-year Treasury note, which typically moves in lockstep with expectations for Federal Reserve rate decisions, sat flat at 4.246%. The benchmark ten-year note held at 4.704%. Neither had budged meaningfully despite the buyback announcements.

Other currencies reflected the mixed signals. The euro edged higher to $1.1668, hovering near a three-month peak it had reached the previous week. Sterling gained 0.1% to $1.3639, also near a six-month high. The Canadian dollar held steady at $1.3844 after slipping 0.6% the day before, as trade tensions between Washington and Ottawa simmered following the collapse of tariff negotiations. The Japanese yen strengthened slightly to 159.21 per dollar, having surrendered most of the gains it had made from recent intervention but still well above the multi-decade low of around 164 that had alarmed policymakers. The Australian and New Zealand dollars both rose 0.1% as traders waited for the Reserve Bank of Australia to release its August policy meeting minutes.

In the cryptocurrency space, bitcoin climbed 1% to $78,817.34, building on what had been its strongest weekly performance in three and a half years. The move suggested some investors were rotating into alternative assets amid the uncertainty gripping traditional currency and bond markets.

What loomed largest for traders, however, was Friday's speech by Federal Reserve Chair Kevin Warsh at Jackson Hole, Wyoming. Warsh was set to make his debut remarks in that role, and markets were hungry for any signal about his thinking on the recent surge in bond yields and, more pressingly, his willingness to operate independently from the Trump administration. Sim Moh Siong, a foreign exchange strategist at OCBC, captured the tension in a note to clients: uncertainty about how the Fed would respond to economic conditions, combined with growing questions about whether the central bank would truly prioritize controlling inflation, had sharpened focus on what Warsh would say. His words could either calm markets or deepen the confusion that was keeping the dollar pinned and yields elevated.