President Barack Obama, pressing for quick Senate ratification of a U.S.-Russia nuclear arms-reduction treaty, summoned a number of former secretaries of defense and state, Republicans and Democrats, to the White House to rally support for the imperiled agreement.

The White House said Obama wanted to discuss at the gathering why it is in the national interest for the Senate to approve the treaty this year, a move that a key Senate Republican says would be premature.

Those invited to the Roosevelt Room meeting Thursday include Secretary of State Hillary Rodham Clinton, Senate Foreign Relations Committee Chairman John Kerry, Sen. Richard Lugar and former Sen. Sam Nunn, plus former secretaries of state Madeleine Albright, James Baker and Henry Kissinger.

Former defense secretaries William Cohen and William Perry and former National Security Adviser Brent Scowcroft also are included. Vice President Joe Biden will preside, and Obama was to drop in on the meeting....