The U.S. dollar struggled to extend an overnight rebound against major peers as investors assessed expanded Iran-related sanctions and efforts to ease pressure on longer-dated Treasury yields. U.S. Treasury Secretary Scott Bessent warned countries to reduce business ties with Iran or risk losing access to the dollar-based financial system. The euro rose slightly to $1.1668 and sterling gained 0.1% to $1.3639, both near recent multi-month peaks. The Canadian dollar held at $1.3844 after a 0.6% decline, while the yen strengthened slightly to 159.21 per dollar. The dollar index was marginally lower at 98.96 after rising 0.16% overnight from three-month lows. Treasury yields received limited support from a report that the U.S. Treasury could use part of its cash balance to buy longer-dated bonds, following Bessent’s announcement that quarterly repurchases would double. The 2-year yield was 4.246% and the 10-year yield 4.704%. Investors are awaiting Federal Reserve Chair Kevin Warsh’s speech in Jackson Hole, Wyoming, on Friday, while bitcoin rose 1% to $78,817.34 after its biggest weekly gain in nearly 3-1/2 years.