The United Federation of Teachers president, Randi Weingarten, has told union leaders she would serve simultaneously as president of the national American Federation of Teachers if she runs for and wins that job.

The presidency of the AFT, one of two national teachers unions, is opening up after its current president, Edward McElroy, announced his intention to retire earlier this year.

Ms. Weingarten, the top and so far only likely candidate to succeed Mr. McElroy, said in an interview yesterday that she would make a final decision whether to run for the position by mid-April. Elections are in July.

If Ms. Weingarten is elected, as is widely expected, she would become the third consecutive UFT president to hold the national and New York City jobs simultaneously. Her predecessors, Albert Shanker and Sandra Feldman, both kept their UFT posts before making the transition to work permanently at the AFT.

Ms. Weingarten said holding both jobs would be the only fair way to ensure the smoothness of her departure from the UFT. An AFT president starts her term the day after being elected, she pointed out, arguing that such abruptness would prevent any smooth transition out of the UFT. “If this happens, I would do both for an uncertain time period,” she said. The period would probably end when Ms. Weingarten felt a qualified successor had emerged to take her place at the UFT. Three have emerged as top contenders: two UFT vice presidents, Michael Mulgrew and Michelle Bodden, and the New York State United Teachers vice president, Maria Neira.

A union representative in the Bronx, Lynne Winderbaum, praised Ms. Weingarten’s decision, saying it would ensure a smooth transition — and more work by Ms. Weingarten in New York. “It’s the best of both worlds,” Ms. Winderbaum said.

Ms. Weingarten has enjoyed broad popularity inside the UFT, consistently winning elections by a landslide. A group of teachers that organizes against her, the Independent Community of Educators, has repeatedly condemned some of Ms. Weingarten’s more unconventional positions, such as her support for performance-based pay for teachers, her support for charter schools, and her new partnership with a charter school operator that bans traditional teacher tenure, Green Dot. The group greeted her announcement, delivered to the union’s executive board and legislative body last week, with disgust. “The UFT deserves a full-time president,” a UFT chapter leader at Jamaica High School who is a member of ICE, James Eterno, said.