U.S. Senator Barbara Mikulski (D-MD) rides an escalator into the subway system at the U.S. Capitol in Washington, January 16, 2014 file photo. REUTERS/Jonathan Ernst

WASHINGTON (Reuters) - U.S. Senate Democrats included $225 million for Israel’s Iron Dome rocket interception system in an emergency funding bill on Tuesday that also cut $1 billion from President Barack Obama’s request for $3.7 billion to deal with thousands of undocumented child immigrants.

“Israel is an essential American ally and needs these assets to defend itself,” said Maryland Democratic Senator Barbara Mikulski, chairwoman of the Senate Appropriations Committee, in a statement.

More than 600 people - most of them Palestinians - have been killed in the current conflict between Israel and militants in Gaza. On Tuesday, Israel pounded targets across the Gaza Strip, saying no ceasefire was near.

Israel said the Iron Dome has intercepted about a fifth of more than 2,000 rockets militants have fired at Israel during the current conflict.

U.S. lawmakers tend to be heavily pro-Israel. However, the fate of the $225 million - and other funding in the legislation - is uncertain in the Republican-controlled U.S. House of Representatives, where there is stiff opposition to an increase in spending tied to the Democratic president’s request.

(This story was fix to correct spelling of Mikulski in paragraph two)