BOSTON — The nation’s top credit card companies on Monday reported mixed progress in reducing the rate at which customers default on their accounts. Higher monthly default rates at Bank of America and Citigroup offset improvements for most other major card issuers.

Analysts said July’s mixed results, along with the recent slowdown in the economic recovery, are unlikely to jeopardize a two-year trend of declining default rates. Most card issuers reported that fewer customers were behind on monthly payments in July. This should lead to fewer defaults late this year.

The higher default rates at Bank of America and Citi “are just monthly noise,” Moody’s analyst Jeff Hibbs said. “The overarching trend of improvement across the industry continues.”

Three of the six top card issuers reported lower default rates in July, compared with the previous month. In terms of late payments, four of six had lower delinquency rates.

Bank of America continues to have the highest default rate among six major card issuers, but it is down substantially from the 14.53 percent the bank reported in August 2009.

The credit card division of Bank of America reported in a securities filing that it wrote off credit card balances at an annualized rate of 7.43 percent last month, up from 6.97 percent in June. The July figure reflects a one-time impact from an accounting change for how to recognize losses in accounts of customers who have died. Excluding that change, July’s charge-off rate would have been 7.14 percent.

Its rate of payments that were late by 30 days or more fell to 4.05 percent in July, from 4.16 percent in June. It was the 10th consecutive month the delinquency rate has fallen.

Citibank, the card division of Citigroup, said its default, or charge-off rate, rose to 6.64 percent annualized for July, up from 6.47 percent in June, snapping a four-month string of decreases. As with Bank of America, Citibank’s delinquencies fell.