President Barack Obama's nominee for his next defense secretary has caused jitters in Israel and hope in Iran for “practical changes.”

The speaker of Israel's parliament, Reuven Rivlin, says he is “worried” about the nomination of former Republican Senator Chuck Hagel because of his stance toward Israel. But Rivlin added that ties between Israel and the U.S. remain strong and “one person does not determine policy.”

Israeli Prime Minister Benjamin Netanyahu and Defense Minister Ehud Barack did not provide immediate comment on Hagel's nomination.

In Iran, foreign ministry spokesman Ramin Mehmanparast said Tehran was hopeful that Hagel's confirmation would lead to “practical changes” to U.S. foreign policy.

Hagel's positions on Iran's nuclear program and relations with the Palestinians appear to be at odds with the Israeli government, and his critics fear his appointment could increase pressure on the Jewish state to make unwanted concessions.

Hagel is expected to face a tough confirmation fight in the Senate.

Mr. Obama nominated Hagel on Monday, along with counter-terrorism adviser John Brennan to head the CIA.

The president called Hagel “the leader that our troops deserve.” He also said the decorated Vietnam war veteran represents “the bipartisan tradition we need more of in Washington.”