BERLIN (Reuters) - Two senior members of Chancellor Angela Merkel’s conservatives on Thursday warned election rivals the Social Democrats (SPD) against politicizing Germany’s efforts to increase military spending, saying security threats made such steps essential.

The strongly worded comments came after Foreign Minister Sigmar Gabriel, a Social Democrat, questioned rapid moves to meet NATO’s defense spending goal, arguing that German spending to integrate a million refugees also strengthened security.

Germany has come under increased pressure since the election of U.S. President Donald Trump to boost military spending to meet NATO’s target of 2 percent of gross domestic product, which was agreed by all members of the 28-nation alliance in 2014.

“The SPD is doing a disservice to Germany’s security by relativising the 2-percent target. The security of our citizens is too important to make it a political football,” said Henning Otte, military spokesman for Merkel’s Christian Democrats and their CSU Bavarian sister party in parliament, and Juergen Hardt, the group’s foreign policy spokesman.

The issue has caused a rift in Merkel’s coalition at a time when the SPD is making gains against conservatives ahead of September’s national election.

German Defense Minister Ursula von der Leyen, also a conservative, issued a statement critical of Gabriel on Wednesday, but the controversy widened on Thursday.

Otte and Hardt said the entire coalition government, including then-Foreign Minister Frank-Walter Steinmeier, an SPD member, had signed the 2 percent goal at the NATO summit in Wales in 2014.

Merkel underscored Germany’s determination to meet the target during a news conference on Thursday, although she has cautioned in the past that it will take time to boost spending from its current level of 1.2 percent of GDP.

Otte told Reuters in a separate statement that it was imperative to increase the size and equipment of the German military to modernize the force and prepare it for new security challenges, not least in the cyber realm.

He said current plans to increase military spending by eight percent year after year would put Germany on a good path to achieve the alliance goal.

Several of von der Leyen’s biggest procurement priorities, including a multibillion-euro missile defense program, a new multi-role ship and a new unmanned drone, have been delayed given rigorous new procurement procedures.