Washington ? Defense Secretary Robert Gates said Thursday he sees no chance that the number of U.S. troops in Iraq will drop to 100,000 by the end of the year, guaranteeing a heavy American military presence as the war grinds into its sixth year to the end of the Bush presidency.

President Bush said Gen. David Petraeus, his top commander in Iraq, can take “all the time he needs” to consider further withdrawals after the latest round of cutbacks is completed in July. In the meantime, Petraeus will continue what, until Thursday, had been secret visits to Middle Eastern countries to try to curb the influx of foreign fighters into Iraq.

With 285 days remaining in his presidency, Bush set the course of the war in a speech following two days of testimony before a skeptical Congress by Petraeus and the U.S. ambassador to Iraq, Ryan Crocker.

Bush said that after the troop withdrawals, which already have been announced, end in July, he would give Petraeus 45 days to evaluate the effects of the drawdown. That would be followed by an indefinite period to reassess U.S. troop strength in Iraq, where new flare-ups of extremist violence are threatening to undercut security gains.

Bush argued that last year’s troop buildup had succeeded in reducing violence, tamping down al-Qaida in Iraq and allowing normal daily activities to resume in many areas. Because of that progress, Bush said, an already planned reduction in troops can be completed in July.

“Serious and complex challenges remain in Iraq, from the presence of al-Qaida to the destructive influence of Iran, to hard compromises needed for further political progress,” Bush said in a White House address. “Yet with the surge, a major strategic shift has occurred. … This war is difficult, it is not endless.”

Petraeus on Thursday revealed for the first time that he had quietly visited several Mideast countries in an effort to slow the flow of foreign fighters into Iraq. The Associated Press learned that the trips, all taken since September, were to Jordan, Kuwait, Bahrain, Turkey and the United Arab Emirates.

Gates appeared before the Senate Armed Services Committee on Thursday and backtracked from testimony he gave last fall when he said he hoped that drawdowns could continue throughout the year, which would have left about 10 brigades – or roughly 100,000 troops – in Iraq at year’s end. When the committee’s Democratic chairman, Sen. Carl Levin, asked Gates whether he still thought that was possible, Gates said: “No, sir.”

In his White House speech, Bush also said he was ordering that Army combat tours be trimmed by three months.

It was a response to heavy pressure from military commanders who say long, multiple deployments have strained the Army to its limits. Army units heading to Iraq after Aug. 1 will serve 12 months instead of 15 months.

Critics of Bush’s war policy noted that the order would not affect U.S. forces already deployed on the front lines.

“The president still doesn’t understand that America’s limited resources cannot support his limitless war,” Senate Majority Leader Harry Reid, D-Nev., said.