WASHINGTON (Reuters) - More than three-quarters of the U.S. House of Representatives signed a letter sent to President Barack Obama Wednesday, insisting that lawmakers play a role in any decision to offer Iran long-term sanctions relief in connection with negotiations on Tehran’s nuclear program.

The letter noted that the U.S. Congress played a central role in enacting sanctions against Iran and insisted Congress be involved in any decision to ease sanctions.

Three hundred and forty-four of the chamber’s 435 members, both Republicans and Democrats, signed the letter, which was released Thursday by California Republican Representative Ed Royce, chairman of the House Foreign Affairs Committee, and New York Representative Eliot Engel, the panel’s top Democrat.

The letter was a strong indication of Congress’ interest in the Iran talks ahead of a July 20 deadline for international negotiators to extend an interim agreement or reach a long-term pact. Many diplomats and analysts believe an extension may be needed in view of the wide gaps in negotiating positions.

Separately, a senior Western official said U.S. Secretary of State John Kerry and foreign ministers from the six powers negotiating with Iran on its nuclear program would travel to Vienna this weekend to help break a logjam in the talks.

U.S. lawmakers, particularly in the Republican-controlled House, are generally skeptical of Iran’s goal in the talks and doubt the Islamic Republic will give up on plans to build nuclear weapons.

The House passed tougher sanctions legislation last summer. But a similar measure stalled in the Senate, where Democrats control a majority of the seats, after the Obama administration said the measure may not give diplomacy a chance to succeed.